How it works Extreme weather

5TOP Overpasses are safe Open windows Stand in the north Outdrive the storm Trailers are targeted
FACTS
1 It may seem a good shelter, but 2 Despite a myth that opening a 3 Tornadoes often come from the 4 The roads will be congested 5 Trailer parks are much more
TORNADO MYTHS highway overpasses act like building’s windows will alleviate south, but standing in the north and covered in debris, and a likely to be damaged by a
wind tunnels and increase the wind pressure, it just lets wind of the house won’t protect you tornado can quickly change tornado, but this is due to
speed of the air. If you are stuck and debris in, and chances are, from debris. Pick a room in the direction without warning. differences in the quality of
in your car in a tornado, get out, the glass will smash anyway centre on the ground floor, Even weak twisters can lift construction rather than any
find a ditch and stay low. when the storm hits. away from any windows. small cars – so don’t drive! natural bias to these abodes.

DID YOU KNOW? Most tornadoes travel from south-west to north-east and occur between 3pm and 9pm

Tornado dynamics Anvil

Take a look at the anatomy of a supercell thunderstorm A flat cloud formation
at the top of the storm;
Cloud dome updraught air slows
down and is forced
The updraught within a outwards by winds.
storm causes air to
overshoot the cloud
top, forming a visible
bulge in the cloud.

Updraughts of warm air carry water droplets Mesocyclone Hail shaft
high into the atmosphere, where they freeze
before being carried downwards by cold A vertical vortex of Frozen water cycles
downdraughts. If they become caught in an rotating air drawn up and down through
updraught again they will refreeze, adding a upwards by convective the storm, growing in
new layer of ice. This process can repeat several updraughts in a storm. size until it becomes
times, generating hailstones that are the size of too heavy to stay up.
golf balls or even larger. Oklahoma was pelted Flanking line
with hail as the storm intensified. Wall cloud
Smaller cloud towers
If there is sufficient updraught to tighten the occur in developed An isolated cloud
central vortex of a mesocyclone it begins to thunderstorms, creating attached to the base of
twist, resulting in a powerful vertical column. a staircase appearance. the storm. Signs of
The inward and outward airflows cause a drop rotation indicate possible
in pressure at the centre, and form what is Tornado tornado formation.

Tornadoes generally 051
form between the
flanking line and the
storm’s main tower.

DEADLY WEATHER

Superstorms

known as a dynamic pipe. At the core of the Geography made for disaster
vortex, the pressure is lowered, which sucks in
more air, causing the column to lengthen and Find out why North America is so prone to twisters
extend down towards the ground.
Cool, dry air Tornado Alley
A tornado warning was issued in Oklahoma
at 2.40pm, and the tornado that ravaged Moore Cold air comes over The states at the
touched down 16 minutes later. It started out as the Rocky Mountains, boundary between cold
a weak EF0 twister, capable of only minor losing its moisture as north-western and
damage to roof shingles, trees and guttering, rain and snow. warm south-eastern air
but within ten minutes it had intensified to EF4. are the most prone to
EF4 tornadoes have extremely destructive WARM FRONT tornadoes in the USA.
winds of up to 322 kilometres (200 miles) per
hour and, on its path to the city of Moore, it COLD FRONT
severely damaged a bridge and killed nearly
100 horses at the Orr Family Farm. Dry line Warm, moist air

Once in the city, the storm intensified to EF5 Dry lines are boundaries found Humid air from the Gulf
– the highest rating for a tornado – and reduced between cold, dry air and of Mexico moves up
many buildings to rubble. It lost its peak warm, moist air. These areas from the south.
strength and returned to EF4 classification, but have high storm activity.
the intensity of the storm caused a great deal
of damage: 13,500 homes were destroyed, or Key features of a storm shelter
damaged, affecting 33,000 people, 24 people
were killed and hundreds more injured. What protection do overground storm shelters offer from extreme winds?

The tornado continued to weaken until it Concrete roof
eventually dissipated at 3.35pm, about eight
kilometres (five miles) east of Moore. A 10-15cm (4-6in)-thick

A pickup truck Steel and concrete roof resists the
wrapped around a plywood door winds that pull other
tree trunk during roofing materials away.
the Moore Tornado Plywood can absorb

impacts, while steel

prevents shrapnel from

penetrating the shelter.

Anchorage Air vent

Shelters are anchored Small ventilation holes
to a concrete slab to allow people to breathe
prevent them from without letting any
overturning in the debris into the shelter.
wind or being swept
away by floodwaters. Reinforced walls

20cm (8in)-thick concrete walls with
internal steel grid supports provide
protection from wind and debris.

Timeline of the Moore Tornado Live tweets from NWS Norman

2.46pm 2.51pm 3.03pm

Storm west of Newcastle is intensifying and showing You DO NOT want to be in your car in a tornado! Stay This is as serious as it gets for SW OKC
some rotation. Stay alert! No tornado warning yet
where you are. Get in, get down and cover up. Tornado and Moore. Please seek shelter now!
052
may affect Moore/south OKC [Oklahoma City]

DID YOU KNOW? Winds in a tornado have been recorded reaching speeds of 480km/h (300mph)!

Chasing tornadoes Turret

Discover the technology that allows the Tornado Intercept Capable of 360-degree
Vehicle 2 (TIV2) to get to the very heart of violent storms rotation, the turret films
high-definition IMAX video
Chassis footage through bullet-
resistant tempered glass
Built around a 2008 and polycarbonate.
Dodge Ram 3500 4x4,
and covered in 3mm Mast
(0.12in)-thick welded plate
steel, the TIV2 weighs in Scientific data,
at 8,000kg (17,500lb). including wind speed,
barometric pressure
and relative humidity,
are collected using a
retractable mast.

Hydraulic skirt Self-levelling
suspension
This can be dropped to
divert wind around the The car has three axles
base of the truck and to capable of maintaining
protect the underside a fixed height above the
from flying debris. road, regardless of
changes in load.

Stabilising spears

A series of 1m
(3.2ft)-long hydraulic
stakes can penetrate the
ground to stabilise the
vehicle in the event of
particularly violent wind.

(@NWSNorman) reporting on the Oklahoma City twister as it played out

3.21pm 3.29pm 3.33pm © Alamy; Corbis

The tornado is so large you may not realise it’s a TORNADO EMERGENCY for Moore SE OKC is in immediate danger! Large violent tornado
moving your way. Do not wait to see the tornado!
tornado. If you are in Moore, go to shelter NOW!
053

DEADLY WEATHER

Firestorms

Firestorms

From tornado-force winds to superhot
flames, dare you discover nature’s
most violent infernos?

054

RECORD 50,000km2 BIGGEST-EVER BUSHFIRE
BREAKERS
The Black Thursday bushfires on 6 February 1851
HOT DOWN UNDER burnt the largest area of any Australian bushfire in
European-recorded history: a quarter of Victoria!

DID YOU KNOW? Large wildfires have increased by 300 per cent in western USA since the mid-Eighties

Firestorms are among nature’s Puffy
most violent and unpredictable
phenomena. Tornado-force winds The cloud has a puffy,
sweep superhot flames of up to 1,000 degrees cauliflower appearance
Celsius (1,800 degrees Fahrenheit) through due to bubbles of rising
buildings and forests alike. Victims often hot air and falling cold air.
suffocate before they can flee and entire towns
can be obliterated. Survivors of firestorms Mushroom cap Smokescreen
describe darkness, 100-metre (330-foot)-high
fireballs and a roaring like a jumbo jet. To give The top of the lower Ash and smoke mask
you an idea of the sheer heat, firestorms can be atmosphere stops the air the base of the cloud
hot enough to melt aluminium and tarmac, rising any farther. Instead and typically turn it a
warp copper and even turn sand into glass. it spreads out beneath. grey or brownish colour.
Firestorms happen worldwide, especially in
the forests of the United States and Indonesia, How do mushroom clouds form?
and in the Australian bush. They occur mostly
in summer and autumn when vegetation is The terrifying mushroom clouds produced that lifts water vapour, ash and dust. The
tinder dry. Although they are a natural after nuclear bombs are examples of vapour starts to cool high in the atmosphere
phenomenon, among the most devastating pyrocumulus, or fire, clouds. This towering and condenses as water droplets on the ash.
were triggered deliberately. During World War phenomenon is caused by intense ground As a result, a cloud forms that can quickly
II, for instance, Allied forces used incendiaries heating during a firestorm. Their tops can become a thunderstorm with lightning and
and explosives to create devastating firestorms reach an incredible nine kilometres (six rain, if enough water is available. The
in Japanese and German cities. Firestorms also miles) above the ground. When the fire lightning can start new fires, but on the
erupted after the cataclysmic impact 65.5 heats the air, it rises in a powerful updraft bright side, rain can extinguish them.
million years ago that many believe to have
triggered the extinction of the dinosaurs. How firestorms change the weather
Climate change may be already increasing
the risk of mega-fires by making summers ever Firestorms can release as much 2. Pyrocumulus 3. Filling the gap
hotter and drier. The Rocky Mountain Climate energy as a lightning storm on a
Organization, for example, has reported that hot summer’s afternoon. The air cools as it rises. Air rushes into the space
from 2003 to 2007, the 11 western US states Moisture condenses onto left by the rising air,
warmed by an average of one degree Celsius (1.7 Warm air above the fire is lighter suspended ash particles creating violent gusts that
degrees Fahrenheit). The fire danger season than the surrounding air so it rises; and a dense cloud forms only intensify the fire.
has gone up by 78 days since 1986. the swirling pillar of lifting air above that can become a storm.
The risk of an Australian firestorm striking a the fire is called a thermal column.
major city has also heightened in the last 40 This tornado-like structure is 1. Thermal column
years. Climate change may have exacerbated responsible for a firestorm’s power.
this by increasing the risk of long heat waves Under the right weather conditions, The fire warms the air
and extremely hot days. In January 2013 alone, air can rise inside the column at above, causing it to
a hundred bushfires raged through the states eye-watering speeds of 270 become lighter than its
of New South Wales, Victoria and Tasmania kilometres (170 miles) per hour! surroundings so it rises.
following a record-breaking heat wave.
Maximum daily temperatures rose to 40.3 Cooler air gusts into the space left
degrees Celsius (104.5 degrees Fahrenheit), behind by the ascending air, causing
beating the previous record set in 1972. violent winds that merge fires
Firestorms can happen during bush or forest together into a single intense entity.
fires, but are not simply wildfires. Indeed, a They also blow in oxygen, wood and
firestorm is massive enough to create its own other flammable material that serve
weather (see boxout). The thunderstorms, to fuel and intensify the blaze.
powerful winds and fire whirls – mini
tornadoes of spinning flames – it can spawn Turbulent air spiralling around the
are all part of its terrifying power. thermal column can spawn fire
The intense fire can have as much energy as tornadoes and throw out sparks.
a thunderstorm. Hot air rises above it, sucking These can set light to trees and
in additional oxygen and dry debris, which houses tens of metres away,
fuel and spread the fire. Winds can reach increasing the conflagration’s range.

055

DEADLY WEATHER

Firestorms

tornado speed – tens of times the ambient wind Firestorm step-by-step Flanking and
speeds. The huge pillar of rising air – called a backing fires
thermal column – swirling above the firestorm See how a deadly firestorm starts as a single
can generate thunderclouds and even spark and spreads rapidly through the forest The fire front burns any
lightning strikes that spark new fires. fuel ahead. Flanking and
Fire front backing fires set light to
The thermal column, in turn, can spawn a vegetation to the sides of
number of fiery tornadoes, which can tower to The fire moves quickly the fire front and behind the
200 metres (650 feet) and stretch 300 metres forward in a long, point of origin, respectively.
(980 feet) wide, lasting for at least 20 minutes. broad curve. Its intense
These fling flaming logs and other burning heat preheats and
debris across the landscape, spreading the dries out vegetation
blaze. The turbulent air can gust at 160 and other fuel ahead
kilometres (100 miles) per hour, scorching of the flames.
hillsides as far as 100 metres (330 feet) away
from the main fire. It’s far more powerful than Spot fires
a typical wildfire, which moves at around 23
kilometres (14.3 miles) per hour – just under the If a fire ignites the
average human sprint speed. tree canopy, the fire
intensifies and burning
Like all fires, firestorms need three things to embers explode many
burn. First is a heat source for ignition and to metres in every direction.
dry fuel so it burns easier. Fuel, the second A similar process is seen
must, is anything that combusts, whether that if you place a dry
be paper, grass or trees. Thirdly, all fires need pinecone into a campfire
at least 16 per cent oxygen to facilitate their – be sure to stand back
chemical processes. When wood or other fuel if you try this though!
burns, it reacts with oxygen in the surrounding
air to release heat and generate smoke, embers
and various gases. Firestorms are so intense
that they often consume all available oxygen,
suffocating those who try to take refuge in
ditches, air-raid shelters or cellars.

Fighting Ignition Crown fires
firestorms
Dried-out vegetation is Fires in the tree canopy,
Fire wardens, air patrols and ignited by a lightning strike, aka crown fires, are
lookout stations all help detect the heat of the Sun or by intense and spread
fires early, before they can human activity – eg a quickly, often threatening
spread. Once a fire starts, discarded cigarette, arson human settlements.
helicopters and air tankers head attack or faulty power cable. Large expanses of forest
to the scene. They spray can be destroyed and
thousands of gallons of water, take decades to recover.
foam or flame-retardant chemicals
around the conflagration. In the
meantime, firefighters descend by rope or
parachute to clear nearby flammable material.
We can reduce the risk of fire breaking out in
the first place by burning excess vegetation
under controlled conditions. Surprisingly this
can actually benefit certain plants and animals.
Canadian lodgepole pines, for example, rely
partly on fire to disperse their seeds. Burning
also destroys diseased trees and opens up
congested woodland to new grasses and
shrubs, which provides food for cattle and deer.
Vegetation in fire-prone areas often recovers
quickly from a blaze. Plants like Douglas fir, for
instance, have fire-resistant bark – although it
can only withstand so much heat. Forest
owners help flora to return by spreading mulch,
planting grass seed and erecting fences.

056

DID YOU KNOW? The biggest man-made firestorm took place in Dresden, Germany, in 1945; 70 per cent of the city was destroyed

Cloud Thermal column Five mega
firestorms
The hot air cools as it Air is warmed by the fire,
goes up, and droplets of becomes lighter than the 1Black Saturday
water condense on the surrounding air and rises In 2009, one of Australia’s
ash particles. A puffy to create a thermal worst bushfires killed 173
cloud forms with pockets column. The lifting air people, injured 5,000,
of billowing, moist air. carries smoke and ash destroyed 2,029 homes, killed
from the blaze with it. numerous animals and burnt
Airtanker 4,500 square kilometres
(1,700 square miles) of land.
Aerial firefighters dump Temperatures may have
water from above, or for reached 1,200 degrees Celsius
more serious blazes, fire (2,192 degrees Fahrenheit).
retardants like ammonium
sulphate are used, which 2Great Peshtigo
also act as a fertiliser to The deadliest fire in
help promote regrowth. American history claimed
1,200-2,500 lives, burned
Wind 4,860 square kilometres (1,875
square miles) of Wisconsin
Sparks and embers flying and upper Michigan and
off the tree canopy are destroyed all but two
blown with the breeze. buildings in Peshtigo in 1871.
They cause the fire to
spread and advance in 3Ash Wednesday
the direction of the wind. More than 100 fires swept
across Victoria and South
Going up Self-sustaining Australia on 16 February 1983,
killing 75 people, destroying
Fires move faster uphill Winds blow in towards 3,000 homes and killing
for several reasons: the the conflagration to 50,000 sheep and cows. It was
flames are closer to fuel replace the rising air. This the worst firestorm in South
sources; vegetation is brings oxygen to feed the Australia’s history.
typically drier on slopes fire. The thermal column
so easier to ignite; and becomes self-sustaining 4Hamburg
winds often blow upslope and a firestorm ensues. This firestorm brought on
because warm air rises. by an Allied bomb strike in
1943 killed an estimated © Alamy; Thinkstock; Peters & Zabransky
44,600 civilians, left many
more homeless and levelled
a 22-square-kilometre
(8.5-square-mile) area of the
German city. Hurricane-force
winds of 240 kilometres (150
miles) per hour were raised.

5Great Kanto
A 7.9-magnitude
earthquake on 1 September
1923 triggered a firestorm that
burned 45 per cent of Tokyo
and killed over 140,000. This
included 44,000 who were
incinerated by a 100-metre
(330-foot) fire tornado.

057

DEADLY WEATHER

Monsoons

Monsoons

The wind systems that reverse seasonally,
bringing dramatically different weather to
subtropical regions

Monsoons are seasonal northern hemisphere. They see
wind systems occurring in the prevailing wind direction
tropical and subtropical and conditions in these areas
regions south, southeast and east of reverse between summer
the large landmasses in the and winter.

Seasonal monsoon conditions Where?
across southern Asia
The major monsoon
Summer systems of the world are

In summer, monsoon winds bring the West African and
heavy rainfall. The land is heated much Asia-Australian monsoons
quicker than the ocean, causing the
warmer air to rise, creating a strong, (marked in red).
large area of low pressure. The cool,
wet air from the ocean is drawn in, Winter
bringing with it warm southwesterly
winds. When the moist air reaches the South Asia’s winter monsoon winds bring
Himalayas, clouds form and produce much dryer, cooler, clearer conditions.
heavy rainfall that can lead to flooding.
Because this time the sea is cooling much
slower than the land, the low pressure © Science Photo Library

and clouds instead form over the ocean,
drawing the cool, dry air from the

mountains into the area. These winter
monsoon winds blow from a
northeasterly direction.

Rain season from the
Panorama Point on
the Matheran Hill

058

5 TOP The thick of it The white killer Fresh snow = bad news Breath of life Intentional avalanches
FACTS
1 A large avalanche might 2 Each year, avalanches kill 3 A snow-faring adventurer is 4 If caught under an avalanche, 5 When a lot of snow builds on a
AVALANCHES release up to 300,000 cubic around 150 people – the most likely to witness an wait for the slide to stop and slope where an avalanche is
yards of snow, which is victims are usually males in impressive avalanche during then use your hands to clear likely, small avalanches are
equivalent to something like 20 their twenties who are or just after a storm that has an area in which to breathe, intentionally triggered using
football pitches covered with experienced mountaineers or deposited around 30cm of then punch a fist upwards explosives to prevent one
ten feet of snow. skiers more likely to take risks. fresh snow. and outwards. potentially deadly slide.

DID YOU KNOW? A noise cannot trigger an avalanche; it’s a myth – a plot device fabricated for films

Avalanche! Interview
What causes these often deadly snow slides?
Cam
Although the potential for an avalanche is present wherever you find a mass of Campbell,
snow on a slope, there are three main types of avalanche each dependent on
several conditions: the type of snow in the snowpack, the temperature, wind, the public
steepness and orientation of the slope, and vegetation (or anchors). avalanche
forecaster for
1. Trigger 2. Starting zone the Canadian
Avalanche
This disturbance is where the avalanche begins to The starting zone is the section of the avalanche Centre, speaks
fracture and it tends to be high up the slope but can still path at which the avalanche is released sending on the dangers
occur anywhere on a mountain. 90 per cent of fatal unsecured snow downhill. It normally occurs on a of avalanches
avalanches are triggered by the victims. steep slope of between 30 and 50 per cent.
What are the most common
The avalanche path 3. Track avalanche triggers?
The most common triggers for all types
This consists of the starting The track is the main path down which an avalanche of avalanches are natural; [including]
zone, the track and the flows. The snow will either slide down as a sheet or loading from new snow, rain or blowing
run-out zone. concentrated in gullies. Towards the bottom of a snow, rapid warming of the snowpack
track you may well see large piles of snow, boulders from an increase in air temperature or
and tree remains. intense solar radiation, falling cornices, or
other natural snowpack stressors. […]
Main types 4. Run-out (debris toe) Most fatal avalanches are human-
of avalanches triggered by the victim or someone in
As the slope flattens out – or meets their party.
Dry (80mph) another slope – the avalanche will come
to rest. This area is the run-out and How and why are avalanches
Occurring below freezing, dry consists of a pile of snow and debris sometimes triggered intentionally?
avalanches are usually triggered by picked up along the run. Any unfortunate [Avalanches are triggered intentionally] to
loading from new snow or blowing victims would likely be found in this area reduce the threat of future uncontrolled
snow. These high-speed slides of deposition. The very end of the avalanches. Any time an avalanche is
consist of air and powdery snow, deposited snow is referred to as the intentionally triggered, strict procedures,
beginning at a single point and avalanche toe. such as access closures and spotters are
gathering speed and mass. As it in place to ensure nobody will be
moves downhill, pressure builds © Science Photo Library adversely affected. Ski resorts or
ahead of the mass of snow, creating commercial backcountry operations
a powerful blast of air capable of often stabilise slopes by triggering
destroying most things in its path. avalanches before opening to the public.
Intentional triggering can be achieved
Slab (60-80mph) safely through remote-controlled
explosives well away from the avalanche
The most common – not to mention path, or hand- or helicopter-deployed
deadly – type of avalanche occurs explosives above the path.
when a layer of compacted snow
overlies softer snow. When the Survival tips
weaker snow can no longer support
the snow above – or if a passing The top ten survival tips for
skier adds to the weight – the hard mountaineers and skiers
layer (usually 30-80cm) will fracture
like a pane of glass and slide away. If Take avalanche safety course
a victim is in the middle of the slab, Read avalanche bulletin
they are unlikely to survive. Choose route or terrain
appropriate for conditions
Wet (10-30mph) Carry and practise using
safety gear (transceiver,
Wet avalanches move slower than shovel and probe)
their drier relatives and occur as a Never travel alone
result of rain or warmer weather Avoid common trigger points
melting the snow. Rain or humidity such as convexities, thin
softens the snowpack, breaking the areas, or below protruding
bonds between water molecules. rocks or trees
Although wet avalanches are slower Travel on avalanche prone
and don’t feature a dust cloud, they slopes one person at a time
are still highly destructive, capable and spot from safe locations
of dragging boulders and even trees If caught do everything in
down the mountainside. your power to escape the
flowing mass
If burial is imminent, create
an air pocket in front of your
face with hands and arms
If buried, remain calm and
await rescue

059

DEADLY WEATHER

Extreme weather

Killer
storms
Marvel at the raw power of
nature at its nastiest

A gust of air rattles the windows. The sky in search of a reprieve. Instead, you see
darkens ominously as coal-black clouds the twister.
creep across the horizon. Thunder
rumbles thickly in the distance accompanied by Mother Nature deserves respect. Before you
the first flickers of lightning, like paparazzi. complain about the light drizzle that spoiled
Suddenly, the rain comes down in sheets, blown your picnic, thank your lucky stars you’ve never
sideways by howling winds. With a crackling experienced a true weather disaster: a six-story
explosion, a tree across the street tsunami wave, 150kph hurricane winds, or
is torn in half by a stroke of lightning. But tornadoes that can toss an 18-wheeler like a
as suddenly as it started, the rain stops. Matchbox car.
The clouds remain low and terribly dark, almost
green. You look out the back window We’ll help you make sense of the Weather
Channel chatter and learn what causes the
world’s most extreme weather phenomena.

The making of a tsunami

How a deep-sea rumble forges a killer wave

On 26 December 2004, a 9.0 magnitude earthquake quake – which released more energy than 23,000 compressed horizontally, it rose vertically,
off the coast of Sumatra, Indonesia triggered a
series of tsunamis – giant seismic sea waves. It was Hiroshima-era atomic bombs – a section of sea floor reaching heights of 30 metres in some cases.
deadliest natural disaster in recorded history.
1,000 kilometres long was pushed ten metres “Tsunamis are not
Tsunamis are not ‘tidal’ waves. They are created horizontally and several meters vertically. ‘tidal’ waves, instead
when a violent geological event – like a submarine
earthquake, landslide or underwater volcanic The violent displacement generated a massive
eruption – displaces a huge amount of water. deep-ocean wave only a few meters high, but

The Indian Ocean earthquake occurred along a hundreds of kilometres long. The almost they are created
subduction zone, a place where one tectonic plate imperceptible swell travelled across the open when a violent
wedges under another. During the record-setting water as fast as a jet aeroplane. As the deep-ocean geological event”
seismic wave neared the shore, it was slowed down
by the quickly rising sea floor. But as the wave

060

DID YOU The most tornadoes…
KNOW?
There are more tornadoes in America than any other country. Supercell
formation is fuelled by warm, moist air from the Gulf of Mexico meeting
cool, dry air blowing over the Rockies.

DID YOU KNOW? on April 3, 1974, when a two-day “Super Outbreak” of 147 tornadoes killed 308 people in 13 states

Tornadoes explained

Why twisters descend from the sky
and drill a path of destruction

Tornadoes are born in beefed-up storm clouds But why do they rotate? It’s down to a precipitation evaporates, releasing pockets of cool
called supercells. While normal storm clouds form phenomenon called wind shear, a sudden change of air that pull downward on the swirling vortex.
and dissipate in 30 minutes, supercells can last for wind speed and direction. Typically, winds blow
hours and spread severe weather across hundreds of faster the higher you climb. This creates a paddle As intensely rotating winds reach the ground,
kilometres. But the most unique characteristic of a wheel effect in the atmosphere, generating columns friction slows the effects of centrifugal force,
supercell is its powerful counter-clockwise rotation. of air that spin on horizontal axes. tightening the funnel. There is incredibly low air
pressure inside the funnel, which acts like a
Supercells start like normal thunderstorms. With supercells, the warm, low-lying air is sucked vacuum. As more and more air is sucked into the
Moist, warm air near the surface is pushed aloft by a up into the storm with such force that it grabs one of vortex, the speed of rotation increases, like a figure
physical force like a cold front. The warm air these horizontally rotating columns of air and twists skater pulling in her arms for the final head-
condenses into water droplets as it reaches higher it vertically. The result is a mesocyclone, an intensely spinning twirl.
altitudes, forming towering clouds. Supercells grow rotating column at the heart of the supercell.
large because of an abundance of warm, wet air Meanwhile, rain and hail falling from the supercell The resulting tornado can generate winds over
below and cool, dry air above. are caught in these rotating winds. Much of the 300mph, tear through reinforced structures like a
buzz saw, lift large vehicles, and flatten homes.

If the sea floor rises suddenly during a violent Tsunamis make landfall as
earthquake, it will displace massive amounts of violently churning walls of
water above, creating a seismic wave. water, sometimes 15 or
even 30 metres high.

A submarine earthquake is Deep-ocean seismic waves have very low Deadly force
more likely to form a tsunami when the amplitude, but wavelengths that can stretch for
focus of the quake the location of the actual hundreds of kilometres. Later waves are usually the deadliest,
rupture – is shallow. launching masses of debris on-shore

As the tsunami approaches the shore, the rising
sea floor compresses the wavelength, greatly
increasing the amplitude.

061

DEADLY WEATHER A combination of the Coriolis force The eye wall – a solid ring of clouds where
and pressure gradient (the rush of rain bands converge and compress – contains
air from high to low pressure), give the hurricane’s most powerful winds.
hurricanes their dizzying spin.

There’s a Image © of DK images
storm
coming…

The origins of hurricanes, a Hot tropical water Some The eerily
deadly force of nature evaporates, rises as meteorologists calm and
vapour and believe storm surges are cloudless eye of the
Hurricanes are massive heat engines. They form over tropical condenses into caused by mounds of hurricane is the point
waters with a minimum temperature of 27˚C (80˚F). Hot water rings of towering water drawn upward by of lowest pressure,
evaporates very quickly, rising up through the atmosphere storm clouds called the low surface pressure in causing air to sink straight
until it condenses into clouds and water droplets. The rain bands. the eye of the hurricane. down toward the ocean surface.
incredible thing is that condensation itself creates even more
heat. The recharged air soars even higher, building a cluster of The hurricane seasons…
towering, fat thunderstorms called a tropical disturbance.
August - June - December
Once the heat engine has been jump-started, rapid October June - November
condensation within the storm continues to force air upward
while more hot air rushes in from below to fill the void. This June - October
suction of hot air from the ocean surface creates lower and
lower air pressure. When air rushes from high pressure to low January - March
pressure, it creates powerful winds. When wind velocity
reaches 38mph, the storm is called a tropical depression. There are few Atlantic hurricanes Hurricanes are October through
hurricanes in the south begin as tropical called typhoons in March is spring and
Satellite images of hurricanes show a swirling vortex of Atlantic because high depressions off the the northwest summer in the
storm clouds. The spin is caused by two main forces: the wind shear near the African coast from Pacific, and they can southern hemisphere,
Coriolis force and the pressure gradient. In the northern ocean surface shreds June to November, occur year-round meaning more
hemisphere, the Earth’s rotation pulls winds to the right tropical storms. when the tropical due to high average cyclones (India) and
(Coriolis force), but the extreme low pressure at the storm’s waters are steamiest. water temperature. willy-willys (Australia).
centre pulls them back to the left, creating a net counter-
clockwise spin. The opposite is true south of the equator. As the Thunder and lightning
heat engine chugs on, more water condenses, more heat rises,
the pressure drops further and spin increases until winds
reach 39 to 74mph, enough to qualify as a tropical storm. Seven
out of ten tropical storms spin even faster than 74mph, officially
becoming a hurricane.

Extreme heat

Hundreds of lightning
bolts strike the earth
every second, each
generating
temperatures
exceeding 27,000˚C

Beauty has never been so powerful…

Inside the chaos of a storm cloud, falling bits and other clouds or points within the same
of ice collide with updrafting water droplets, storm cloud. In fact, only ten per cent of
shearing off electrons to create newly lightning strikes hit the earth. Cloud-to-
charged particles. The negative particles ground lightning begins when a negative
sink to the bottom of the cloud, while charge from the cloud begins to carve a path
positive particles rise to the top, just like a of least resistance through ionised air,
colossal battery. As a storm cloud swells in zigging and zagging every 25 meters. When it
size, the force of its negatively charged nears the ground, a positive charge called a
underside repels negative ions away from ‘streamer’ reaches up from surface objects,
the surface of the Earth, creating a net completing the circuit. The resulting strike is
positive charge on the ground. Something instantaneous, travelling at 300 million m/s
needs to correct the imbalance between with the power of 100 billion volts.
theses huge oppositely charged masses.
A clap of thunder is caused by shock waves
Lightning is a violent electrical discharge created by the expanding and contracting
between clouds and surface objects, clouds air around the superheated lightning.

062

5 TOP The world’s most No-holds-barred A four-ce to be Another myth down A name to be
FACTS powerful generator Nancy reckoned with the drain remembered

HURRICANES 1 If you calculate the total heat 2 Typhoon Nancy, which tore 3 Only twice in modern history – 4 It is untrue that the Coriolis 5 Since the Fifties, all tropical
generated by condensation across Japan in September 1893 and 1998 – did four force causes toilets to flush in storms and hurricanes in the
inside a hurricane, it equals 1961, clocked sustained winds hurricanes power their way different directions in the Atlantic basin receive a name.
200 times our daily worldwide of 185kph (213mph), the simultaneously through the northern and southern If the storm’s particularly
energy-generating capacity. fastest on record. Atlantic basin. hemispheres. deadly, the name is retired.

How are Thesedeadly
blizzards winterstorms

can strike

created? without
warning

In January 1996, 100 million tons of snow fell on the streets of New York City
and nearby Philadelphia was buried under a record 78 centimetres (30.7
inches). Ice storms and sub-zero temperatures stretched as far south as
sunny Florida, trapping people in their homes, often without electricity. In
1891, easterly winds dumped 3.6 metres (11 feet) of snow in London. Trains
were completely buried under tremendous drifts and 65 ships sank under
the heavy ice and snow.

Blizzards form exactly like thunderstorms. A cold front pushes warmer,
moist air into the atmosphere, condensing into clouds. If temperatures
stay below freezing, snow falls instead of rain. If huge amounts of snow are
accompanied by gale-force winds, it’s possible to achieve a complete
whiteout, when earth and sky merge in a disorienting canvas of white.

DID YOU For a winter storm to qualify as a blizzard, there Blanket covering!
KNOW? must be sustained winds of at least 58kph
(35mph) and less than 0.4 km (0.25 mile) visibility You’re going to need more than an ice
for three hours or more. scrapper to get out of this one mate…

Waterspout

While it’s never truly rained ‘cats and dogs’, it has rained frogs and fish. In Water world
the past century, towns in the United States, Greece and Serbia have been
inundated with falling amphibians (some of them frozen solid) that pile up You know you’re in trouble when your
in the streets. While a Biblical plague isn’t out of the question, the more street looks more like a river than a road
likely culprit is a waterspout, a tornado-like vortex that forms over water.
Floods After the rains, the deluge
There are two kinds of waterspouts: tornadic and fair weather. Tornadic
waterspouts form under the exact same conditions as tornadoes and can When you think of killer weather, you picture tsunami-battered coasts or
generate winds over 300kph (200mph) with powerful internal updrafts. twisting black tornadoes. But one of the deadliest weather phenomena
The low-pressure core of the waterspout can dip several metres under worldwide is flooding. Flash floods – where small rivers and creeks swell
water, sucking up anything in its path, including fish, frogs and lizards. without warning to raging torrents – are the number one weather-related killer
Fair weather waterspouts grow from the ocean up, created by the sudden in the United States. Flash floods can happen almost anywhere. In cities, there
convergence of smooth and choppy seas. Swirling water is pulled upward often isn’t enough green space to absorb the runoff from a severe storm. This
by rising air currents, without the help of a major storm system. can overwhelm drainage systems, causing flash floods in low-lying areas.

While fair weather waterspouts are weak and rarely cause damage, In the mountains, a sudden torrential downpour can feed hundreds of small
tornadic waterspouts have torn apart ships at sea. Famed waterspout streams that merge in a single river valley. The result can be dramatic and
researcher Joseph Golden believes many so-called ‘Bermuda Triangle’ deadly, creating a wall of churning water – five to ten metres of mud, rocks and
disappearances are caused by killer waterspouts. debris – that wipes out everything in its path. Violent hurricane winds – gusting
over 135kph (155mph) in some cases – can push a mound of water in front of the
The walls of a waterspout are hurricane called a storm surge. During Hurricane Katrina, powerful surges
semi-transparent, since they breached the levee system, causing widespread destruction by flooding.
are made of windswept water,
not dirt and debris The 2007 floods in the UK were an example of river flooding caused by
sustained, powerful rains. Over the course of 12 hours, parts of northeast
England received a sixth of their annual rainfall, swallowing whole towns in
swollen rivers.

063

FODisOFcoRvNeCrAEEaTrStUh’sRnaEtural forces

66

66 Earth’s extreme 76 Where does acid rain
climates
come from?
Discover the Earth’s amazing
diversity of climates Discover the origin of this

eroding rain

70 How do jet streams 77 Hailstones
work?
Understand what makes these
Find out what jet streams massive balls of ice that rocket
actually do to the ground

72 La Nina 78 How insects survive
73 floods
74 Explaining the Pacific Ocean
weather extremes Discover what happened to
insects when flash flooding
The science of wind invaded their home

Learn about the invisible force “A lot of different
we experience every day factors play into the
different climates
Supercell thunderstorms present on Earth”

Why do these blinding flashes
and rumbles occur?

064

FORCES OF NATURE

78

74

72

065
© Andrew Mandemaker 2006
© DFID; Thinkstock

FORCES OF NATURE

One planet, many climates

Mount Herschel in Antarctica,
which has been affected by
global warming

© Andrew Mandemaker 2006

Earth’s extreme
climates

From dry, polar deserts to wet, hot rainforests and everything
in between, Earth has some amazing extreme climates

Climate goes far beyond weather. It belt or cell, with its own unique characteristics. either side of the equator, temperatures can vary
explains why there are such predictably They are considered the ‘weathermakers’ for widely in part because the proximity of the Sun
disparate regions on the Earth and such the latitudes they occupy, as they both affect changes more drastically with the Earth’s tilt and
wide variations in things like temperature, and are affected by temperatures on the rotation. Once you reach the Poles, we’re back to
precipitation, humidity, wind, vegetation and Earth’s surface. extremes, with temperatures that are consistently
plant life. There are a lot of different factors that cold due to the distance from the Sun.
play into the different climates present on our Each of the five main lines of latitude – Arctic,
planet, and they work together in a complex Tropic of Cancer, the equator, Tropic of Capricorn and Topography also affects climate, and can
way. One is the differences in how air circulates the Antarctic – also have a big impact on the climate supersede other factors. One striking example of this
around the Earth. Depending on where you are in which you live. Most areas near the equator are is California, which boasts several major different
located, you are in the path of a different wind hot, as the Sun is directly overhead with very little types of climate all in one state (some of which even
variation in temperature. As you move outwards on have sub-climates). There is a Mediterranean

066

THE TOP
STATS
58°C 27.2°C 22,987mmTEMP
FASTEST in 15 min TOP
TEMP DROP RAINFALL

EARTH’S CLIMATE

>20million ~485km/h -89.2°CRECORDS
MOST YEARS TOP WIND LOWEST
WITHOUT RAIN SPEED TEMP

DID YOU KNOW? Most extreme climate claims are disputed, due to variations in instrument accuracy and possible human error

Atmospheric Westerlies Polar cell
circulation
These winds blow predominantly from west to The Polar cells are the
Atmospheric circulation is the way east in the middle latitudes, between 30 and 60 northern and southernmost
that the Sun’s energy is dispersed degrees north and south. wind belts circling the Earth.
across the Earth’s surface. This
large-scale air movement behaves in Trades High-pressure areas come
predictable patterns and follows from cold air circulating
specific cycles, creating different These north-easterly
climates across the globe. and south-easterly over the Poles, which heats
winds blow from and rises as they move
their respective outwards and create
directions and get low-pressure areas.
stronger in the
winter during times
of high pressure at
the Poles.

© NASA The Doldrums are found Ferrel cell
in the intertropical
convergence zone Unlike the other
cells, the Ferrel cell
is not a closed loop.

It is known as the
‘zone of mixing’,

where the air from
the Polar cells
and Hadley
cells converge.

© DK Images Hadley cell

Intertropical When warm, humid air rises near
convergence zone the equator, it travels towards the

This area in between the Poles and descends into a
various types of prevailing low-pressure area.
winds is very calm, with little
The Lut desert boasts the to no wind. Changes in latitudes,
hottest surface temperature changes in attitudes
recorded on Earth

climate along the coast and in some of speculated that we could be headed for Latitude – whether you’re north or south of the equator – has a huge impact
the interior valleys. A desert climate is another ice age. However, today the on a region’s climate. At the equator and the poles are the most extreme
present in dry valleys and mountain prevailing theory is that the Earth will temperatures: very hot due to a lot of incident sunlight, or very cold due to a
ranges. Other areas of high elevation experience a climate change due to low amount of sunlight. The ‘in between’ areas, or ‘middle’ latitudes,
have more temperate climates and vary global warming. While believers in the generally have definitive seasons and wider ranges in temperature.
depending on proximity to the ocean. next ice age did not specify human
California even has areas of steppe, a involvement, global warming North Pole Arctic circle
type of grassland. High temperatures theorists point to an increase in
across the state can reach 38°C (100°F) and greenhouse gases as a cause for rising Sun’s rays Marks the beginning of the
lows can get down to -11°C (12°F). Thanks temperatures around the globe. These Arctic region and changes
to its coast and the Andes, the country of gases absorb and emit radiation, and are depending on the Earth’s tilt.
Chile can also boast a number of a result of an increase in carbon dioxide Once a year there’s a 24-hour
different climates within its borders. in the Earth’s atmosphere due to burning
Both California and Chile have fossil fuels. day and a 24-hour night.
numerous examples of micro-climates
– areas where the climate can vary Another possible cause for climate Tropic of Equator
widely within square kilometres, thanks change is deforestation, which has Cancer
to differences in topography. already affected climates in areas such The Sun passes
as rainforests. There is a general This was named directly over the
The Earth has undergone extreme consensus among the scientific when the Sun
climate shifts in its history, one such community that the Earth’s surface appeared overhead equator at the
being the ice ages. Ice ages are periods temperatures increased by 0.74°C (1.33°F) in the constellation March and
when the temperature of the planet as during the last century. The possibility of Cancer during the September
a whole has gone down enough to overall climate change to the Earth as a June solstice.
create more alpine ice and polar ice whole, however, remains controversial equinoxes, its rays
sheets. In the Seventies many scientists among the general public. perpendicular to

the Earth’s surface.

Tropic of Capricorn South Pole Antarctic Circle

The Sun appears directly This circle marks the beginning of the
overhead during the December Antarctic and also experiences one
solstice. To the north, until you
reach the Tropic of Cancer, is the 24-hour day and one 24-hour night per
tropical region. year at the solstices.

067

FORCES OF NATURE

One planet, many climates COLD! Snag, Yukon, Canada STILLEST

Climate zones Lowest recorded temperature of Rising air
-63° C (-81°F).
The Earth’s climates can be classified The Doldrums
into different zones that have similar WET! Mount Waialeale, HI, USA
conditions, vegetation, types of Sailors travelling through this
seasons and temperatures Average annual rainfall of 11m (36ft). region near the equator, known as
the intertropical convergence zone
Polar/tundra (ITCZ), called it ‘The Doldrums’
because the air is so still. Rather
Generally the tundra has one month with than blowing as wind, air rises due
an average temperature of 0°C (32°F), but to convection as it is heated by the
no months with an average high greater Sun. This is generally located about
than 10°C (50°F). There is low rainfall and five degrees north and south of the
snowfall, and vegetation comprises dwarf equator, but can move as much as 45
shrubs, lichen and grasses. degrees in either direction. The
ITCZ is where the north-east and
Examples: Alaska, northern Canada south-east trade winds converge,
and Russia, Greenland, Iceland and creating an area of low pressure.
northern Scandinavia.
COLD! North Ice, Greenland
Boreal/coniferous forest
Lowest recorded temperature of
Boreal/coniferous forests are usually in -66°C (-87°F).
areas of higher elevation, between 900
metres (2,953 feet) and 1,300 metres © Hannes Grobe 2007 CALM! Oak Ridge, TN, USA
(4,265 feet) above sea level. There is a high
level of both rain and snowfall and very Average annual wind speed of
cold temperatures. 7km/h (4mph).

WINDY! Chicago, IL, USA

Known as the Windy City but
not even the windiest in the US.

WINDY! Mount Washington, USA

Holds the North American & Western
Hemisphere Record for highest recorded

wind speed.

CALM! Walla Walla, WA, USA

Average annual wind speed 9km/h
(5.1mph).

Examples: Uplands of New England, HOT! Death Valley, CALM! Talkeetna, AK, USA
inland Canada and Alaska, northern Arizona, USA
Norway, much of northern Asia. Average annual wind speed of
Highest recorded 8km/h (5mph).
temperature of 57°C (134°F).

Mountain DRY! Batagues, Mexico WET! Debundscha, Cameroon

Mountain regions are above the tree Average annual rainfall of 3cm Average annual rainfall of 10m (34ft).
line – the line at which trees stop growing (1.2in).
due to extreme cold or dryness. High WET! Quibdo, Columbia
elevations mean colder temperatures
because air expands when it rises. There Average annual rainfall of 8.9m (29.5ft).
are strong winds and there is usually a lot
of snowfall.

Examples: Rocky Mountains, Himalayas,
Alps, Pyrenees, Andes.

Temperate/ DRIEST WINDIEST
deciduous forest
Dry by the sea A special kind
As its name implies, this climate is of wind
very moderate, with distinct Arica, Chile
seasons. Summer highs can reach Commonwealth Bay,
32°C (90°F) and a winter lows can The Atacama desert is the driest Antarctica
reach -1°C (30°F). Rainfall and region on Earth, and Arica is the
snowfall can vary widely. driest city. There are regions that With an annual mean wind speed
have not received rainfall in tens of of over 80km/h (50 mph) and winds
Examples: Eastern and millions of years. Arica itself regularly topping 240km/h (149
western United States, Canada, receives about 0.75 millimetres (0.03 mph), this is the windiest place on
Europe, West Asia. inches) per year, and once went a Earth. Katabatic wind also occurs,
span of 173 months without rainfall. where cold air rushes down a steep,
068 Despite this, Arica’s average annual ice shield from the rocky point of
high is only around 27°C (80°F). Cape Denison towards the water.

DID YOU © NASA Extreme climate on other planets
KNOW?
Mars is the most Earth-like when it comes to climate, with a summer
high of 20°C (68°F). However, the average daytime temperature is -50°C
(-58°F). There’s also the little problem of no air, very little surface pressure
and no magnetic field.

DID YOU KNOW? Increases in global temperatures can result in more extreme weather events, like tornadoes and hurricanes

HOTTEST WETTEST Mediterranean

Toasted wheat Water, water! Although it is generally centred around
the Mediterranean basin, this climate
Lut desert, Iran Mawsynram, India exists in other parts of the world that are
near warm bodies of water. There are cool,
This large desert basin comprises The wettest place actually varies wet winters and hot, dry summers due to
mostly salt, sand and rock. Its title between Mawsynram and the subtropic air pressures.
as the hottest place on Earth is in nearby city of Cherrapunji, with a
dispute, but according to NASA difference of less than 1,000 Examples: Mediterranean, California,
satellite measurements in 2005 the milimetres of annual rainfall. western and south Australia, parts of
average land temperature is 71°C Mawsynram in north-east India has central Asia.
(159°F). Surrounded by mountains, it an average annual rainfall of nearly
is considered a dry drainage basin. 12 metres (39 feet). Mawsynram is in Desert
One area is known as Gandom the Khsai Hills and about 1,400
Beriyan, Persian for ‘toasted metres (4,593 feet) above sea level. The main defining characteristic of
wheat’, due to a story that spilled Air blowing in from nearby plains deserts is the lack of precipitation – most
wheat scorched in just a few days. cools as it rises, trapping moisture get less than 250mm (10in) per year. Many
in clouds, which release their rain are so dry that there is a moisture deficit
COLD! Oimekon, Russia during monsoon season. and very little vegetation. Deserts are
thought of as hot and sandy, but there are
Lowest recorded temperature polar deserts as well.
of -68° C (-90°F).
Examples: Arabian, Sahara, Gobi,
HOT! Al Aziziyah, Libya Kalahari, Antarctic, Arctic.

Highest recorded Temperate grassland
temperature of 58°C (136°F).
These areas have no large trees, just
HOT! Tirat Zvi, Israel grasses and shrubs. There are wide
variations in temperature. Winter lows
Highest recorded can reach -40° C (-40°F) and summer highs
temperature of 54°C (129°F). can go up to 38°C (100°F). Rainfall averages
50cm (20in) per year.
DRY! Wadi Halfa, Sudan
Examples: Prairies of North America,
Average annual rainfall of steppes of Europe, pampas of
0.25cm (0.1in). South America.

COLDEST © historicair Tropical
grassland/savannah
Cold and ice DRY! McMurdo Dry
Valleys, Antarctica Savannahs have grassy areas with widely
Vostok, Antarctica spaced tree cover. There is generally just
Snow-free valleys that have one rainy season that can produce up to
Vostok Station is a Russian research likely never received rain. 150cm (59in) of precipitation over the space
station at the southernmost Pole of of as little as a few weeks. Average
Cold. The coldest air temperature WINDY! Wellington, NZ temperature is 30°C (86°F).
recorded was at Vostok, at -89°C
(-129°F). Vostok is on the centre of Known as Windy Wellington; Examples: African savanna, northern
the east Antarctic ice sheet, which is gusts up to 160km/h (37mph). Australia, southern United States.
one of two polar ice packs on Earth
and holds about 60 per cent of the Tropical rainforest
Earth’s fresh water. There’s no
moisture in the air, wind speed is Tropical rainforests are found within 28
high, and it’s at an altitude of 3,500 degrees north or south of the Equator.
metres (11,483 feet). It also has a Annual rainfall is about 200cm (80in)
night that lasts 130 days. All of this and the average temperature is always
makes research very challenging. above 20°C (68°F) no matter what time of
year. There is a dense tree canopy and
little undergrowth.

Examples: Africa, Asia, Australia, Central
America, South America.

069

FORCES OF NATURE

Jet streams explained

How do jet Earth’s jet streams

A closer look at some of the invisible phenomena
that play a major role in our planet’s climate

streams work? Polarcell
They’re a vital component in regulating global
weather, but what do jet streams actually do?

Jet streams are currents of fast-moving air found Ferrel cell
high in the atmosphere of some planets. Here on Subtropical jet
Earth, when we refer to ‘the jet stream’, we’re
typically talking about either of the polar jet streams. There Hadley cell
are also weaker, subtropical jet streams higher up in the
atmosphere, but their altitude means they have less of an
effect on commercial air traffic and the weather systems in
more populated areas.
The northern jet stream travels at about 161-322 kilometres
(100-200 miles) per hour from west to east, ten kilometres (six
miles) above the surface in a region of the atmosphere known
as the tropopause (the border between the troposphere and
the stratosphere). It’s created by a combination of our planet’s
rotation, atmospheric heating from the Sun and the Earth’s
own heat from its core creating temperature differences and,
thus, pressure gradients along which air rushes.
In the northern hemisphere, the position of the jet stream
can affect the weather by bringing in or pushing away the
cold air from the poles. Generally, if it moves south, the
weather can turn wet and windy; too far south and it will
become much colder than usual. The reverse is true if the jet
stream moves north, inducing drier and hotter weather than
average as warm air moves in from the south.
In the southern hemisphere, meanwhile, the jet stream
tends to be weakened by a smaller temperature contrast
created by the greater expanse of flat, even ocean surface,
although it can impact the weather in exactly the same way
as the northern jet stream does.

Hadley cell

This atmospheric cell is partly
responsible for the deserts and
rainstorms in the tropics.

Winds of change Subtropical jet

Currents in the jet stream travel at various speeds, but the These winds are much higher
wind is at its greatest velocity at the centre, where jet in the atmosphere than their
streaks can reach speeds as fast as 322 kilometres (200 polar counterparts, at around
miles) per hour. Pilots are trained to work with these 17,000m (55,000ft).
persistent winds when flying at jet stream altitude, but
wind shear is a dangerous phenomenon that they must be Southern polar jet
ever vigilant of. This is a sudden, violent change in wind
direction and speed that can happen in and around the jet The southern hemisphere’s
stream, affecting even winds at ground level. A sudden jet stream runs around
gust like this can cause a plane that’s taking off/landing to the circumference of the
crash, which is why wind shear warning systems are Antarctic landmass.
equipped as standard on all commercial airliners.

070

RECORD FASTEST WIND IN THE WEST
BREAKERS
The highest terrestrial wind speed ever recorded was in April
BLOW ME DOWN!
372 1934 on Mount Washington, USA, where a very strong jet
km/h stream descended onto the 1,917m (6,288ft) summit.

DID YOU KNOW? Mount Everest is so high that its 8,848m (29,029ft) summit actually sits in a jet stream

Northern polar jet Where is the
jet stream?
Travelling west to east
around the northern A layer-by-layer breakdown of
hemisphere, it helps keep
northern Europe temperate. the Earth’s atmosphere and

whereabouts the jet stream sits

Ferrel cell

These cells are balanced by the
Hadley and polar cells, and
create westerly winds. They are
sometimes referred to as the
‘zone of mixing’.

Polar cell

These north-south
circulating winds bring
in cold air from the
freezing poles and
produce polar easterlies.
© SPL
© NASA

071

FORCES OF NATURE

Understanding La Niña

La Niña explained

How this Pacific Ocean phenomenon is responsible for weather extremes

La Niña is defined by What happens during La Niña?
unusually cold ocean
temperatures in the See how a period of cooler sea temperature can have far-reaching effects
equatorial Pacific. It’s caused by a
build-up of very cool water in the Normal Walker circulation cell
tropical Pacific, which is brought to year
the surface by easterly trade winds This is the name given to the airflow seen
and ocean currents. This upsurge in the tropics during normal conditions
of water causes sea-surface and La Niña, but is reversed during El Niño.
temperatures in areas near South
America to drop drastically. Normal rainfall
La Niña can trigger changes in
rainfall patterns, atmospheric Rainfall in this location is
circulation and atmospheric common, but is less frequent
pressure, having dramatic effects than during La Niña.
on the global climate. La Niña
events are associated with Normal trade winds
cataclysmic flooding in Northern
Australia. In 2010, they resulted in These blow in the same direction
arguably the worst flooding in during La Niña, but weaken or even
Queensland’s history, causing reverse during El Niño (where ocean
more than two billion Australian temperatures are warmer than usual).
dollars’ worth of damage and
requiring the evacuation of over Moist air rising La Niña trade winds
10,000 people. La Niña does have
some positive effects, however, Moist air rises from the During La Niña the equatorial
often boosting the South American warm water but cools once trade winds become even
fishing industry due to the it reaches South America. stronger, warming Australian
upwelling of nutrient-rich waters, waters as they blow east to west.
where fish populations thrive.
Although our understanding of La Niña Stronger
La Niña has grown, forecasting it is year upwelling
still difficult, even when
combining the latest satellite and Increased rainfall The stronger
marine buoy data. With such a upwelling around
global impact, every effort is being Rainfall increases in the western South America
made to find a way to predict this Pacific due to low-pressure causes deep, cold
age-old phenomenon. zones, but decreases over the water to rise to the
eastern Pacific. surface, providing
nutrient-rich
waters that boost
fish populations.

The devastation caused by La Niña in
Queensland was unprecedented;
thousands of homes were destroyed

Warmer Australia Equatorial thermocline Cooler South America

In Australia, sea temperatures La Niña results in the equatorial La Niña causes the sea temperature
are found to be warmer than thermocline steepening, due to around South America to drop,
average during La Niña. upwelling in South American waters. cooling by 3 to 5°C (5.4 to 9°F).

072

The science of wind

It’s invisible but we see and feel its effects every day, so just what is wind?

Winds are the air currents in
Earth’s atmosphere that move due
to changes in pressure. When the
Sun’s energy heats the surface of the Earth,
the air mass overhead becomes warmer and
less dense, which causes it to expand and
rise. Air masses typically cover millions of
square kilometres. Because there is now less
air pressing down on the Earth, an area of
low pressure develops. To maintain balance,
the nearest mass of cooler, higher-pressure
air automatically moves into the lower-
pressure area to fill the gap. The movement
of this air mass is wind. The greater the
difference in air mass temperature, the more
intense the wind blows. Remember, air
always flows from an area of high pressure to
an area of low pressure.

Low- and high-
pressure zones

1. Warm air rises

Warm air molecules move around
more than those of cold air. As the
molecules now have greater orbits
they also take up more space and so
the mass of air expands.

2. Low pressure forms

Because there is now less air
pressing down on the Earth, an area
of low pressure occurs.

4. Wind © Science Photo Library

We can feel the movement of this
cold air sinking beneath the rising
warm air as wind.

3. Cold air
replaces warm air

A colder air mass moves into the
space that the warm air
originally occupied.

073

FORCES OF NATURE

Supercell thunderstorms

Supercell Inside a
thunderstorms superstorm

Why do those blinding flashes What turns a rainstorm into a
and ominous rumbles occur? supercell thunderstorm?

Thunderstorms are both ANVIL 12,200m / JETSTREAM
spectacular and a bit scary, 40,000ft
but what creates this
awe-inspiring mix of rain, thunder Thunder 9,150m /
and lightning? On warm days, hot air 30,000ft
forms near the Earth’s surface. As hot air is The rapid heating and
less dense than cold air, it rises, pushing expanding of the air Fully charged
through the colder air above it. Eventually it around the lightning
cools enough for the moisture contained inside creates a thunderclap. Water particles lose
the air to condense. As the moisture in the air electrons as they move
turns to liquid, it forms ice crystals. These ice through the cloud.
crystals are dense, so they become heavier
than the updraft and begin to fall down 6,100m /
through the cloud. As they descend toward 20,000ft
Earth they thaw and become rain.
When the water particles move through the Lightning
cloud, electrons are stripped from them.
Positively charged particles sit at the top of the The negative
cloud and negatively charged particles remain charge of the cloud is
at the bottom. This induces a positive attracted to the positive
charge on the Earth’s surface below, so charge of the ground.
the clouds are desperate to hand over Electrons get transferred in
their spare electrons. Once the charge a flash of lightning.
has built up, the electrons from the
cloud power toward the ground,
discharged as a spark of electricity that we
see as a bolt of lightning. As lightning can
travel at a breakneck 160,000 kilometres
(100,000 miles) per hour, it creates a lot of heat.
This causes the air around the lightning to
expand extremely quickly, creating vibrations
that we hear as thunder.
Supercell thunderstorms are formed when
thunderstorms and high winds collide and
combine, causing what is called a mesocyclone.
This will often lead to a tornado forming, as the
rapidly rotating wind combines with the
updraft to create a weather system that pulls
objects upward with tremendous force. High
precipitation supercells are the worst kind of
them all, as the tornado is hidden behind a wall
of water, making it tricky to spot and avoid. On
top of it all, the heavy rain makes flash floods a
real risk.

074

DID YOU KNOW? Supercell tornadoes can bring hail more than 1.9cm (0.75in) in diameter

Mesocyclone

This upward, rotating motion
creates a mesocyclone, which
forms inside the stormcloud.

Moisture

Moisture in the air
condenses, bulking
out the cloud. This
steadily turns into
ice crystals.

Warm air rises The stormcloud of a supercell
thunderstorm is an impressive sight
As warm air is denser
than cold, it rises up Different
through the types of
atmosphere until it thunderstorm
reaches the clouds.
Single cell storms
High winds Single cell storms are the
weakest kind. They usually last
If the storm meets less than half an hour and don’t
high winds, the cause much damage because
updrafts pull the wind there isn’t much horizontal
around the cloud. wind to push them along.

Warm air Multicell cluster storms
You will see multicell cluster
The Earth and the storms more than any other.
air above it is This is when several storm cells
warmed by the Sun. combine, acting at different
times in the cycle, so as one
Rain Tornado stops raining, another begins.
As they are all separate, though,
The ice thaws and falls The mesocyclone can also strong tornadoes are rare in
as rain. If it doesn’t form a tornado, which can this type of storm.
thaw, it falls as hail. uproot buildings and vehicles
in its powerful vortex. Multicell line storm
A long line of storms is called a
Thunderbolt facts multicell line storm. It’s also
known as a squall line and
forms when a group of storm
clouds are led along a route by a
strong, sustained gust of wind.
Cold air on the outside of the
system forces warm air rapidly
upward, resulting in incredibly
heavy downpours of rain.

Hot! Powerful! Loud! Fast! © The Art Agency; Dreamstime

The air around The five billion Thunder can Tornadoes can
lightning joules of energy be as loud as move at over
heats to a in a single 120dB. This is 113km/h
scorching lightning bolt loud enough (70mph), which
27,760°C (50,000°F). This could fulfil a home’s to be heard over the is as fast as the highest
is five times hotter than electricity needs for a crashing guitars of a current speed limit on
the surface of the Sun. whole year. rock concert. British motorways.

075

FORCES OF NATURE

Acid rain

Where does acid rain come from?

We’ve all seen the effects of acid rain on limestone statues,
but how does this damaging substance form?

All rainwater is a little bit acidic, also be harmful to crops, as well as polluting Fossil-fuelled power stations and petrol/diesel
because the carbon dioxide present in waterways. It forms in the atmosphere
the atmosphere dissolves in water when poisonous gases emitted by human vehicles give off chemical pollutants – mainly
and forms carbonic acid. Stronger acid rain, activities combine with the moisture within
however, can damage stone structures and can rain clouds. sulphur dioxide (SO2) and nitrogen oxides (NOx) –
which when mixed with the water in the air react

and turn acidic.

Acid rain in action 3. Gasses dissolve Oxidation of sulphur
and nitrogen
Upon combining with the water vapour (water and
oxygen) in the rain clouds, the gasses react to form

weak but potentially damaging acid. Sulphur
dioxide from industry becomes sulphuric acid.

2. Wind Sulphur
dioxide (SO )
The gases are carried on the
wind to higher ground, 2
towards rain clouds.
This is a by-product
of heavy industry,
such as power
stations.

Nitrogen oxides (NOx)

These are released in car
exhaust fumes.

KEY:

Blue: Nitrogen
Yellow: Sulphur

Red: Oxygen

4. Acid rainfall 1. Acidic gases © Science Photo Library

When acid rain falls it can Sulphur dioxide and nitrogen
damage plant life, infiltrate oxides from industry and
waterways and erode buildings vehicles are released into
and statues. the atmosphere.

007766

Hailstones

The balls of ice that fall to the ground, ruining crops, denting cars and smashing greenhouses

Hailstones form in the upper parts of hailstone in half. Most hailstones are about the creating another layer of ice. As the hailstone grows
freezing storm clouds which feature very size of a marble, but can occasionally be as large heavier, it falls back down through the cloud,
powerful convection air currents that as oranges. colliding with yet more ice particles on their way up.
stretch up to ten kilometres into the atmosphere.
They consist of many layers of either clear, hard ice, Water droplets form inside storm clouds and are The hailstone can circulate around the cloud
or softer milky snow, formed under different drawn upwards by strong rising air currents where many times, gaining more and more layers of ice,
they turn into ice. On its journey up, an ice particle until it becomes too heavy for the air current to
conditions, which can be will bump into even colder water particles – they support. At this point it will drop out of the cloud
seen if you slice a then stick together and gain in size and weight, completely, falling to earth.

Hailstone formation

Some hailstones can Circulating air
reach the size of an orange currents

Downdraught The movement of powerful
convection currents sends
When the hailstone can no water particles whirling up
longer be supported by and down and up and down
the rising warm air through the cumulonimbus
current, it will descend cloud, where they fuse with
with the falling cool air and other particles and gain in size
drop out of the sky. until the stone is too heavy to

remain airborne.

Strong updraught

The temperature at the base
of the cloud is warmer than at

the top, causing powerful
rising air currents that send
ice particles higher where it is
colder. They collect more and
more frozen particles adding

to their size and weight.

077

FORCES OF NATURE

Surviving floods

How insects
survive floods

Discover what happened when flash flooding
forced creepy crawlies to take to higher ground

This photo taken by the UK’s Department
for International Development (DFID),
following an unprecedented monsoon
season in Pakistan, reveals the dramatic effect
severe flooding can have on local environments.
In July 2010 the same amount of rain that would
typically fall in a decade fell in a week in southern
Pakistan, and the water didn’t recede for months.
The extent of the flood spanned an area the size of
the UK and forced the local wildlife – including birds,
animals and insects – to seek refuge on higher
ground. Four months later something remarkable
began to happen: all the trees and other plantlife in
the region started to develop ghostly white veils of
silk. Millions of spiders, as well as other bugs, were
spinning webs in the trees high over the water.
An interesting reported side effect of this unusual
natural phenomenon was that, despite the fact the
water was receding slowly and leaving massive
pools of stagnant water, mosquito numbers
remained relatively low. This was unusual because
still water conditions are ideal for helping complete
the mosquito life cycle. Authorities had therefore
expected the mozzie population to soar; instead
numbers were down. The mosquitoes were thought
to be getting ensnared in these blankets of silk. This
positively impacted on public health by reducing the
incidences of malaria in the area as a result.

078

STRANGE How do spiders sometimes Answer:
BUT TRUE make a quick getaway?
Spiders can get airborne by spinning a single strand
EIGHT-LEGGED A Ballooning B Paragliding C Diving of silk and waiting for a breeze. When the velocity
ESCAPE ARTIST of upward air flow causes drag that exceeds the
pull of gravity an arachnid can take off on the
breeze, a phenomenon known as ballooning.

DID YOU KNOW? A farm in Australia was also overrun when subterranean wolf spiders sought refuge from flood water

© DFID; Thinkstock

079

SPACE
WEATHERDiscover the weather from outer space

90

82 Wildest space weather 89 Weather on Jupiter
Understand the craziest Find out about the weather on
weather phenomena that the largest planet and what is
occur in space different to us

86 What is space weather? 90 Deadly solar storms
How does space have weather How explosions on
in no atmosphere? the Sun affect us here on Earth

87 Why is Venus so hot? 94 Solar tornadoes
Where does Venus’ high Discover the story behind the
temperature come from? twisters that take place on
the Sun
87 Solar tsunamis
Learn about these mega- 96 Extreme space
waves of energy temperatures
Get to grips with the highest
88 Amazing Martian and lowest temperatures
weather recorded in space

Weather on Mars: dust “Weather isn’t just a
devils to carbon dioxide ice phenomena on Earth”
fans discovered

080

SPACE WEATHER

89

94

96 82

081
© NASA; JPL; SDO; SPL © NASA
© NASA; Corbis

SPACE WEATHER

Wildest space weather

We complain about Weather on Earth can be
the weather here extreme, but whatever’s
on Earth, but happening outside right
weather on other now where you are, it’s a safe bet
planets is on a that it’s better than the weather in
whole other scale the rest of the Solar System.
of extremes Earth has the nicest weather
thanks to a number of features: its
size, its distance from the Sun, its
axial tilt, orbital and rotational
period, and its chemical
composition. Although Earth’s

082

RECORD LARGEST STORM ON SATURNIn April 2013, the Cassini spacecraft imaged a storm on Saturn
BREAKERS
unlike anything seen before. At 2,000km (1,240mi) across, it could
STORMY SATURN
2,000km cover the UK over 12 times and had winds up to 530km/h (330mph).

DID YOU KNOW? In 1989, geomagnetic storms caused an electrical blackout in Québec, Canada, that lasted 12 hours

meteorology can be devastating, One factor all of the planets have phenomenon that is common and That’s not even the strangest
in comparison to some of our in common is the Sun and its rather pedestrian on Earth has weather in the Solar System. While
planetary neighbours, it’s actually emissions. The heliosphere is much greater repercussions on studying it can be difficult, our
rather mild. Plus, a lot of our considered a part of the Sun’s Venus. A type of solar wind called history of flybys, missions and
weather can be summed up in one atmosphere, but it extends beyond a hot flow anomaly (HFA) causes probes are helping us to create
word: water (albeit in various Pluto, about 19 billion kilometres massive explosions of energy, but detailed models of climate on
forms). Meanwhile, on planets (12 billion miles) from the star. on Earth it’s deflected by the other planets like Mars. Learning
lacking water, an atmosphere or a magnetosphere. However, Venus about similar effects on other
magnetic field to shield them from So Earth does have some has no magnetosphere, so the planets – even in their more
the worst of the Sun’s radiation, weather in common with other explosions can cover the entire extreme form – is helping us better
you have to wonder why we’re so planets. In February 2014, planet. Not that it was particularly predict and prepare for changes in
keen to visit any of them! researchers at NASA’s Goddard hospitable anyway. weather on Earth.
Space Flight Center discovered a

Jupiter’s Great Dust storms can drastically raise Dust storms on Mars
Red Spot the temperature, as the particles
trap heat in Mars’s atmosphere Earth’s deserts have nothing on the Martian
One of the defining features of the Solar landscape when it comes to dust storms. The Red
System’s biggest planet is a storm located about Planet is so dry, dusty and rocky that its dust
22 degrees south of the equator in the South storms can last for weeks. These storms develop
Equatorial Belt (SEB), commonly known as the quickly and can cover vast regions of the planet.
Great Red Spot (GRS). Astoundingly, the GRS Because the Martian atmosphere is so thin,
has been raging for more than 400 years, and is superfine particles of dust rise in the air as heat
located at a higher altitude and measures from the Sun warms the atmosphere. Mars has
colder than the surrounding cloud layer. It such an eccentric orbit that its seasons are
rotates anticlockwise, making one full rotation extreme; temperatures can be as low as -143
every six Earth days and is currently as large as degrees Celsius (-225.4 degrees Fahrenheit) and as
two Earths across. The storm has shrunk by high as 35 degrees Celsius (95 degrees Fahrenheit).
half its size in the past 100 years – at one point During Martian summers, when the temperature
its diameter was measured at more than 40,000 swings the most at the equator, dust storms are
kilometres (24,855 miles). more likely to develop.

The GRS is different from storms on Earth Saturn’s hexagonal jet stream
because the heat generated within the planet
continually replenishes it. Hurricanes on Earth Jet streams are generally circular, but Saturn likes to
dissipate when they make landfall, but Jupiter
is gaseous, so the storm rages on. Jupiter’s be different. The Voyager mission made an especially
atmosphere is composed of cloud belts that
rotate due to a system of jet streams. The interesting discovery in the early-Eighties when flying
northern side of the storm is bordered by an
eastward jet stream and the southern side by a over the planet’s north pole. It’s surrounded by a jet
westward jet stream. These hold the storm in
place as it makes laps around the planet. stream that’s not circular but hexagonal. Each side

Despite the high winds around it, there’s of this immense hexagon is estimated to be
little wind inside the storm. Its colour is
probably caused by sulphuric compounds and around 15,000 kilometres (9,321 miles) long
varies from white to dark red, and sometimes it
isn’t visible at all. These colour changes seem and it has a 30,000-kilometre (18,640-mile)
to correspond to colour changes in the SEB, but
without any predictable schedule. diameter. It surrounds a vortex and

Has lasted over rotates at the same rate as Saturn (a day
4,700x longer than
Earth’s longest storm on Saturn is about ten and a half hours).

In order to explain this unusual

feature, University of Oxford

physicists re-created it in a

laboratory. They used a cylinder of

water to serve as the planet’s

atmosphere with a ring inside it to

represent the jet stream (with

green dye to make it visible). The

cylinder was placed on a spinning

table and the ring spun faster

than the water. The faster the

ring spun, the less circular the jet

stream became. By varying the

speed and the differences

between the rotations of the water 4x Earths could fit inside
and the ring, different shapes
appeared. So the theory is that the

rate at which this particular jet

stream spins in relation to the

Saturnian atmosphere is what leads to

the odd hexagonal cloud formation.

083

SPACE WEATHER

Wildest space weather

What role does You can find out whether it Saturn’s diamond rain
the Sun play in rains any other gems in space
space weather? in Brain Dump on page 84 Some researchers believe that lightning storms on
Saturn could result in diamond precipitation – as
There are numerous factors that affect much as 1,000 tons each year. The theory is that
weather on each planet in the Solar lightning zapping the methane in the atmosphere
System, but they all have one thing in releases carbon atoms from the gas. These carbon
common: the Sun. Two main types of solar atoms stick together and drift down towards the
activity take place in the Sun’s atmosphere planet’s core. As the pressure and temperature
that have far-reaching effects. Coronal mount, the carbon is compressed into graphite and
mass ejections (CMEs) and solar flares can eventually diamonds that could be as big as a
wreak havoc on a planet. CMEs are bursts centimetre (0.4 inches) in diameter.
of magnetic fields and solar winds that
release matter and electromagnetic However, when the diamonds reach the core –
radiation. Solar flares are massive bursts where temperatures can be as hot as 7,727 degrees
of light and energy that release atoms, Celsius (13,940 degrees Fahrenheit) – the
ions, electrons and radiation. A CME gemstones would melt into a liquid state.
usually follows a solar flare.
Violent Neptunian winds
These energy surges from the Sun can
result in solar energetic particles (SEPs), The outermost planet in our Solar System has some 5x stronger than
highly energised particles including seriously extreme weather in general, but what really gusts on Earth
electrons, ions and protons that can travel blows astronomers away is its wind. In fact, Neptune
as fast as 80 per cent the speed of light. is home to the strongest gales anywhere in the Solar
SEPs and other matter and radiation that System, topping out at over 2,100 kilometres (1,300
reach Earth cause geomagnetic storms miles) per hour – about the speed of a fighter jet. By
that can have a variety of effects. comparison, winds on Earth generally max out at 400
kilometres (250 miles) per hour. These powerful
They cause the stunning polar auroras, winds move in a direction opposite from the rotation
but other effects are less desirable. In the of the planet. There are two different theories for
case of solar flares, there’s an increase in what causes these winds. One idea is that although
the amount of UV radiation in the Earth’s they’re very powerful, these winds remain high up in
atmosphere, which can affect the the atmosphere, in a layer no more than 1,000
movement and longevity of satellites by kilometres (600 miles) thick. This means that the
making the atmosphere denser. They can processes causing these winds are also shallow, likely
cause interference and disruption of due to the condensation and evaporation of moisture
communications and navigation on the in the atmosphere. The other theory is that these
surface, while particles from flares can processes are much lower in the atmosphere, caused
damage delicate electronics on satellites or by the meeting of the heat generated from within the
the International Space Station. They can planet as its core shrinks as it meets the extreme cold
even cause changes in the Earth’s climate. at the surface (below -200 degrees Celsius/-328
degrees Fahrenheit). If the winds do prevail deeper
into the atmosphere, they may also be so intense
because the planet’s featureless surface contains
nothing to slow them down.

Jupiter’s electric auroras

The auroras on Earth get a lot of attention for their forces charged particles (ions) into the atmosphere,
beauty, but Jupiter has auroras larger than the entire which causes a reaction that results in beautiful
Earth. In fact, they produce nearly a million light displays. One potential source for the ions is
megawatts of energy! And unlike Earth-based Jupiter’s moon Io, but scientists aren’t quite sure
auroras, they’re always happening. On Earth, the how this happens. Ultraviolet images of the auroras
light displays are caused by solar storms, but reveal not just their blue glow, but also three blobs
Jupiter’s auroras are self-generated. As the planet of light. These are Galilean moons Io, Ganymede and
rotates, it generates electricity at its poles and Europa as they interact with Jupiter’s magnetic field.

Jupiter’s auroras have been
described by some scientists
as ‘northern lights on steroids’

084

STRANGE What would happen if you Answer:
BUT TRUE stood on Venus and it rained?
Although rain on Venus is corrosive sulphuric acid, the
RAIN, RAIN, GO AWAY A You’d melt B You’d smell funny C Nothing surface heat is so intense (480°C/900°F) that the rain
evaporates before reaching it. Of course, acid would
be the last of your worries with that intense heat and a
surface pressure 90 times greater than Earth’s!

DID YOU KNOW? Solar flares can release energy equivalent to the explosion of millions of 100-megaton hydrogen bombs

Titan is home to Top five
methane rain weather
satellites
Titan looks Earth-like thanks to its abundance
of lakes, rivers and clouds. But appearances GPM – Launch: 2014
can be deceiving; instead of a water cycle,
Saturn’s largest satellite has a methane cycle. The Global Precipitation
Seasonal rains fill the moon’s basins, the Measurement will
contents of which evaporate and condense into provide 4D views of
clouds that once again release rain. hurricanes, rainstorms
and even falling snow on
Titan’s methane Earth. It will be used for both
cycle in focus long-term climate research and
provide live weather forecasts.
Titan has a methane/ethane cycle that
follows the seasons, similar to the monsoon DSCOVR – Launch: 2015
rains in some places on Earth
The Deep Space Climate
Precipitation Cloud formation Observatory satellite will spot
space weather (like solar flares)
Precipitation in the form Emissions from the that could be damaging to
of methane rain falls and volcanoes and vapour Earth. DSCOVR will be in an
fills the lakes, starting the from the lakes rise and orbit 1.5mn km (932,000mi)
cycle again. condense into clouds. away to escape some of the
Earth’s magnetic effects.
Surface lakes Volcanic degassing
SOHO – Launch: 1995
The massive lakes on the Methane gas is released
surface of Titan are from the moon’s interior The Solar and Heliospheric
mostly clustered near its through volcanic activity. Observatory mission is in a
north pole and are halo orbit around the
relatively shallow despite Evaporation Earth. SOHO was
having a great expanse. commissioned to study
The methane and ethane the Sun, but it has also
gases evaporate from the discovered more than
lakes as the seasons 2,000 comets.
change on Titan.
CASSIOPE – Launch: 2013
© NASA; JPL; SDO; SPL
The Cascade Smallsat and
Ionospheric Polar Explorer is a
small satellite specifically
designed to gather data on
solar storms that affect the
Earth’s upper atmosphere and
cause auroras as well as
magnetic interference.

SST – Launch: 2003

The Spitzer Space Telescope
observatory is unusual
because it has a heliocentric
orbit, slowly drifting away from
Earth. In its extensive studies
of stars, the SST has discovered
space weather on some of
the smallest stars
around, known as
brown dwarfs.

085

SPACE WEATHER © NASA

Space weather

What is
space
weather?

There’s no atmosphere in
space, but it still has weather

Just because we have an atmosphere
here on Earth, it doesn’t mean we have
a monopoly on weather. Outer space
has weather of sorts too, and it’s driven by the
same source – the Sun. When we refer to space
weather, we’re generally talking about what’s
happening on the Sun and what the solar wind
is doing. At key points during its 11-year solar
cycle, the Sun releases billions of tons of solar
material in what is called a coronal mass
ejection (CME), which can cause huge magnetic
storms around the Earth. This can make for an
impressive northern and southern lights
displays known as auroras.

086

Ancient volcanoes Why is Venus
contributed to Venus’s so hot?
atmosphere and might
still be erupting today. The hottest planet in
the solar system’s
© ESA/AOES Medialab runaway greenhouse
© NASA/ESA/LMSAL effect explained
Solar tsunamis
The mega-waves of energy that tear across the Sun With a surface temperature of 462°C,
Venus is definitely not the ideal holiday
Solar tsunamis, also known as The tsunamis are formed when the Sun destination. Its unique climate
Moreton waves or fast-mode emits a coronal mass ejection (CME), a massive contributes to the most powerful greenhouse
magnetohydrodynamic (MHD) burst of solar wind commonly associated with effect in the solar system, with an atmospheric
waves, are surges of material sent crashing solar flares. Around the ejection point a pressure 92 times that of Earth. It’s thought that
across the Sun as the result of a solar flare circular wave extends outwards in all billions of years ago the planet was much like
being launched into space. They can travel directions travelling at a super-fast rate. Earth, with a significantly lower temperature and
up to an incredible 1.6 million kilometres vast oceans of water. However, its proximity to the
(1 million miles) per hour. In February 2009, the two STEREO Sun meant this liquid water evaporated into the
Solar tsunamis are made of hot plasma and spacecraft watched as a billion-ton cloud of gas atmosphere. This in turn sublimated carbon in
magnetic energy. The first was observed by was hurled off the surface of the Sun from a rocks and mixed with the oxygen in the
Gail Moreton in 1959, and since then several CME. The result was a solar tsunami that atmosphere to form carbon dioxide, which now
more studies have been conducted on the towered 100,000 kilometres (60,000 miles) high accounts for about 95 per cent of the atmosphere.
phenomenon by the Solar and Heliospheric speeding across the star’s surface at about This is known as a ‘runaway greenhouse effect’,
Observatory (SOHO) and the Solar Terrestrial 900,000 kilometres (560,000 miles) per hour. as the creation of more carbon dioxide in the
Relations Observatory (STEREO) spacecraft. Estimates indicate it contained the same atmosphere released more carbon from the
energy as 2.4 million megatons of TNT. ground, repeating the process. Only 10 per cent of
incoming solar radiation reaches the surface, but
almost all of this stays trapped inside the
atmosphere, giving rise to a temperature
difference of almost 500°C between the surface
and the cloud layer.

Solar tsunamis can
be thrown away

from the exit point
of a solar flare as it’s

ejected into space

087

SPACE WEATHER

Martian weather

Amazing Martian weather

From dust devils to carbon dioxide ice fans, Mars sees some weird phenomena

Martian dust devils are one example tornadoes. Indeed, they are so powerful that Another prominent feature on Mars that is
of the unusual weather found on the they leave a visible trail of chaos in their wake, driven by its seasons is the sublimation (rapid
Red Planet. A dust devil is a ‘skinny’ in the form of huge snake-like streaks. vaporisation) of carbon dioxide ice near the
whirlwind that on Earth forms when hot air planet’s surface. This occurs when Mars’s
near the surface rises rapidly through a pocket Talking of dust, the dust storms on Mars have seasonal winter caps of frozen carbon dioxide
of cooler, lower-pressure air and begins to the ability to shroud the entire planet in a are quickly heated and transformed into
rotate. This creates a spinning column of air violent gauze of particulate matter moving at vapour in spring. The gaseous CO2 then escapes
– typically 10-50 metres (33-164 feet) in height – 145 kilometres (90 miles) per hour-plus that can through gaps in the ice, carrying dust with it,
that has enough energy to suck up surface dust. reduce visibility to less than five per cent of and is spread by local winds over the surface,
Martian dust devils are in a different league that under normal conditions. often into distinctive fan shapes.
to those on Earth. Typically 50 times as wide
and often several kilometres high – as well as These epic storms form in the planet’s Mars also has clouds like Earth. These
boasting intense rotational energy that can southern hemisphere during the spring and clouds, however, generally form much higher
suck up vast quantities of dust and rocks – dust summer seasons. Activity is first heavily in the atmosphere than ours (ie 80-100
devils on Mars are more akin to super- localised, however when the amount of carried kilometres/50-62 miles up) and are made of
dust reaches a critical quantity, the storm carbon dioxide. They are also very faint,
Rock fragments and dust rapidly intensifies and spreads, carried to the resembling mesopheric clouds, and can only
are collected from Mars’s far-flung reaches of the Red Planet through form around minuscule grains blown high into
surface and transported to strong jet streams at speeds commonly in the atmosphere during dust storms.
its farthest reaches by excess of 100 metres (328 feet) per second.
powerful jet streams Martian dust devils cruise
across the planet’s surface,

leaving a serpentine tail of
dust and rock in their wake

An example of carbon
dioxide sublimation at the
planet’s polar ice caps

© NASA

088

AVERAGE

140,000km 16,500km 10DIAMETER
THE GREAT RED HOURS
STATS SPOT SIZE IN A DAY

JUPITER 360 35,500°C-145°CLOWEST
AVERAGE
WIND HIGHEST
TEMPERATURE SPEED km/h TEMPERATURE

DID YOU KNOW? 17th-century astronomer Giovanni Cassini called the Great Red Spot the “Eye of Jupiter”

Weather on Jupiter

The forecast is raging storms and swirling winds

If you’ve ever moaned about the Fahrenheit). And if that doesn’t sound quite bad can be more than 360 kilometres (224 miles) per
weather, then you can count yourself enough, then the weather conditions on the hour. For comparison, Earth has two prominent
lucky that you don’t live on Jupiter. The surface of the planet are almost guaranteed to eastward jets in each hemisphere and their
majority of the planet is formed of hydrogen and put you off. average speed is about 100 kilometres (62 miles)
helium gases. The clouds, however, are made up per hour.”
of ammonia ice crystals. We spoke to expert Pedram Hassanzadeh, an
The temperature range on Jupiter is pretty Environmental Fellow at Harvard University: If, having seen the wild temperature changes,
incredible. The clouds that hover above the “The atmosphere of Jupiter has two prominent the mind-boggling winds and dramatic
surface of the planet are a freezing -145 degrees visible features”, he explains. “These are strong tornadoes, you are still keen to visit Jupiter,
Celsius (-229 degrees Fahrenheit), but as you winds that form multiple jets of alternating Hassanzadeh has one more word of advice for
move closer to the core it reaches a scorching direction between the equator and the poles, any potential tourists: “Jupiter does not have a
35,000 degrees Celsius (63,000 degrees and hundreds of hurricane-like swirling winds solid surface, which would make life on the
known as vortices. The average speed of the jets planet kind of hard.”

The Great Temperature Vortices
Red Spot
The temperature of Jupiter The winds swirling in
One of the best-known features of can range from a chilly opposite directions
Jupiter, apart from its size, is the -145°C (-229°F) to a create vortices,
Great Red Spot. First recorded in super-hot 35,000°C which are rapidly
1831 and consistently observed for (63,000°F). rotating tornadoes.
more than 100 years, the weather
system measures about 16,500 x Composition Rotating jets
14,000 kilometres (10,250 x 8,700
miles). Hassanzadeh explains what The majority of Jets of wind move in
the Great Red Spot actually is: “It Jupiter is made alternating directions,
consists of strong swirling winds up of hydrogen whipping up storms such
with a maximum speed of 700 and helium gas. as the Great Red Spot.
kilometres (435 miles) per hour. It’s
not clear how the Great Red Spot Ammonia crystals
was created, but vortices are
common in rapidly rotating Above the surface of
environments such as the Jupiter is a thick layer of
atmosphere of the gas giants.” cloud made up of
ammonia ice crystals.
The Great Red Spot is notable as
it has been raging for centuries, Core
much longer than any other similar
space tornadoes. However, It’s thought Jupiter
Hassanzadeh has a theory as to could potentially
how it has kept going for so long: “It have a solid or
has been speculated that the Great molten core.
Red Spot has survived by extracting
potential energy from the
atmosphere and the kinetic energy
of the jets, along with absorbing
smaller vortices.”

Winds © NASA; Corbis

Winds on the planet can
reach up to 700km/h
(435mph), driven by the
rotating jets.

089

SPACE WEATHER

Deadly solar storms

Deadly
solar
storms

Discover why huge explosions
from the Sun can cause major
problems on Earth

Weather isn’t just a
phenomenon for Earth’s
atmosphere; there’s an entirely
different type of weather occurring out
in the space between Earth and the Sun,
thanks to changes in the latter’s
magnetic activity cycle. Among other
things, this cycle modulates powerful
outbursts from the Sun’s surface that
can have a direct impact on our lives.
These are known as geomagnetic, or
solar, storms.
Solar storms can also include a wide
range of related phenomena, including
auroras and electromagnetic emissions
as well as solar energetic particle events,
solar flares, and coronal mass ejections.
Some of these have little effect on Earth.

090

5 TOP Black hole sun Solar tsunamis Loop the loop Parker spiral Somersaulting Sun
FACTS
1 The Sun gets holes in its 2 Solar flares generate massive, 3 Cooled plasma can loop 4 Thanks to the influence of 5 During the solar maximum,
WEIRD SOLAR corona. These areas are darker fast-moving shock waves on 700,000km (435,000 mi) from solar wind, the Sun’s the Sun’s poles switch – the
ACTIVITY andcolderthan the surrounding the corona known as Moreton the Sun’s surface in a formation magnetic field takes on the north pole points south and
area and have open magnetic waves. They can move as fast known as a solar prominence. shape of an arithmetic spiral vice versa – as increased
field lines, allowing for solar as 1,500 kilometres (932 They can break off and form as it rotates and extends sunspot activity causes its
wind to develop. miles) per second. coronal mass ejections. throughout the solar system. magnetic field to change.

DID YOU KNOW? Some estimate that a super solar storm could cause $2 trillion USD in damage

Solar minimum The solar
cycle
When the Sun is quiet during the solar
minimum, the surface of the Sun Sunspots are temporary dark spots of
sometimes goes for hundreds of days intense magnetic activity on the Sun’s
without a single sunspot. surface. They change according to a cycle
that lasts roughly 11 years. Clustered into
Solar maximum two bands around the Sun’s mid- All Images © NASA
latitudes, they move closer to the equator
During this period of high solar over the course of the cycle. During the
activity, the number and cycle, the period of fewest sunspots is the
frequency of sunspots and solar solar minimum, while the time of
flares is at its peak. greatest activity is the solar maximum.
This cycle has been a quiet one, with 50
Coronal mass ejection per cent less activity than predicted.
and solar flare However, astronomers believe we are
now approaching solar maximum, with
The energy released is millions of times the apex occurring in 2013, and wonder if
greater than a volcanic eruption, the Sun might make up for lost time with
resulting in CMEs and solar flares more intense solar storms.
(clouds of highly charged atoms, ions
and electrons).

Not all solar storms
affect Earth

Magnetic field lines Solar
Flare
North and south magnetic field
lines break through the Sun’s
surface near sunspots and
reconnect in loops, resulting in a
massive burst of energy.

For example, charged particles driven resulting radiation can damage DNA Depending on the velocity at which it astronomer who first viewed it, this
into the Earth’s upper atmosphere by and increase astronauts’ risk of was released, a CME can reach the storm started with a solar flare. This
solar wind impact with atoms and cancer and other diseases. At high, Earth’s magnetosphere, or magnetic led to a CME that travelled to Earth in
create the beautiful, luminous glow prolonged doses, exposure can lead to field. The highly charged particles of 18 hours (as opposed to the three or
known as the auroras in the high- death. In addition, the sensitive solar wind can be powerful enough to four days that they typically take).
latitude areas of the Northern and instruments on spacecraft can be cause a shock wave and disturb the Because we’re so reliant upon high-
Southern Hemisphere. However, not affected, causing problems with magnetosphere. The resulting release tech electronic systems, powerful
all space weather phenomena is navigation or power. Very high-energy of plasma and radiation, while not solar storms like the Carrington Event
innocuous – some can even be fatal. A solar proton events can theoretically biologically dangerous (our have the potential to cause serious
solar proton event (SPE) has the ability even harm passengers on high- atmosphere absorbs the most damage. Subsequent storms have had
to endanger the life of astronauts. altitude aircraft flights. harmful radiation), can disrupt serious effects. In 1960 there was
SPEs are a type of cosmic ray that everything from power grids and oil another solar storm that caused
occurs in conjunction with other solar But what happens when an event drilling on the ground to widespread radio blackouts. A more
storm phenomena such as solar flares. has a direct impact on us here on communications and GPS satellites in intense storm in 1989 left 6 million
Comprising electrons, protons, and Earth? A coronal mass ejection (CME) the atmosphere. people in the dark in Quebec when a
heavy ions that are extremely high- occurs when the Sun releases a huge power grid failed – but we have yet to
energy, some SPEs can be as fast as 80 burst of charged particles known as In 1859, the largest solar storm ever experience another superstorm like
per cent the speed of light. The solar wind, along with plasma and recorded hit Earth. Named the that in 1859.
radiation, from a cluster of sunspots. Carrington Event in honour of the

091

SPACE WEATHER

Deadly solar storms

Geomagnetic superstorms

Solar flares and coronal Solar wind
mass ejections
This continuous stream of charged
These two of the most powerful solar particles from the Sun pushes matter to
phenomena can release the same Earth, approximately 150 million
energy as millions of 100-megaton kilometres (93 million miles).
hydrogen bombs.

Sun

Solar storms occur when
magnetically active areas of the Sun
located around sunspots are
super-heated, ejecting masses of
plasma, gas and charged particles.

“CMEs can release 100 billion kilograms
of highly charged particles”

Super-strong
storms

Solar storms and the resulting The largest solar storms emit 10 million times © OliverSpalt
phenomena can be amazingly more energy than a volcanic explosion
powerful, especially solar flares and
coronal mass ejections. Solar flares and
CMEs can release the same amount of
energy as millions of 100-megaton
hydrogen bombs exploding at once. The
largest ones emit up to 1032 ergs, which
is 10 million times the energy released
during an average volcanic explosion on
Earth. CMEs can also release 100 billion
kilograms (220 billion pounds) of highly
charged particles at a speed of 1,000
kilometres (621 miles) per second.

092

HEAD DEADLY 1. Ultraviolet DEADLIER 2. Electromagnetic DEADLIEST 3. X-Class
radiation radiation solar flare
2HEAD © Jen, 2009
Exposure to UV rays can The loss of power and An astronaut standing on
<OKI<D< JLE cause skin cancer, including communications from a severe the moon during these
<==<:KJ melanoma, which accounts solar storm has the potential to strongest of solar flares
for 75 per cent of skin cause numerous deaths around could die instantly from
cancer deaths. the world. radiation poisoning.

DID YOU KNOW? During the Carrington Event, some telegraph operators could still send messages due to the storm’s currents

Earth Super solar
storm effects
Depending on the strength of the
solar flare or CME, it can take up to The Carrington Event, the most severe prevents reflection, rendering radios
three days to reach Earth. solar storm ever recorded, wreaked useless. Air heated by intense
havoc from 28 August to 2 September ultraviolet emissions would rise and
Auroras 1859. Telegraph systems in North increase the density of the gasses in
America and Europe were disrupted low-Earth orbit, putting drag on
When the charged particles interact by the powerful electrical currents. satellites stationed there and causing
with Earth’s magnetosphere, they are They electrocuted telegraph operators, them to slow down or even fall out of
deflected towards the poles and while snapped wires sent out sparks orbit entirely. The flood of charged ions
down into the atmosphere. and set fires. Intense red and green and electrons would also cause
auroras were reported in places they’d electronic overloads, either damaging
never been seen before, including the or disabling the satellites entirely.
Rocky Mountains and the Caribbean. Electronic currents entering power
lines could overload transformers and
A storm like the Carrington Event generators and blow them out. Travel
would have a much greater effect on would come to a standstill as planes
our society. Radios, for example, rely would be unable to navigate and
on reflections of waves off the ionised power grid failures could leave people
gas in the Earth’s ionosphere. Intense in the dark for weeks or even months.
radiation disrupts the gas and

The main effects of Auroras are just one of many
a solar superstorm effects of a solar superstorm

Magnetosphere › 8lifiXj
› IX[`f Xe[ KM YcXZbflkj
The magnetosphere shields Earth › DfY`c\ g_fe\ kfn\i ]X`cli\j
from the most deadly effects of solar › 8jkifeXlkj Xe[ jXk\cc`k\j Xk i`jb
storms, deflecting the charged › Gfn\i ^i`[ ]X`cli\
particles away from the planet. › E\knfibj f]Õ `e\
› G_Xekfd Zlii\ekj `e gfn\i c`e\j
› ?Xi[nXi\ [XdX^\[
› 8`i kiXm\c Zi`ggc\[
› 9Xeb`e^ jpjk\dj [fne
› <ogcf[`e^ ^Xj c`e\j

Space weather
forecasts

NASA has several different spacecraft magnetic activity, UV output and Between NASA, the US Air Force, the ESA and
and satellites in place to report on images from near Earth. Finally, the JAXA, there are 16 different heliophysics
space weather. These include two satellite known as ACE monitors solar missions currently in operation
spacecraft orbiting on opposite sides of wind and radiation, with the ability to
the Sun, known as STEREO (Solar give a 30-minute warning before a
Terrestrial Relations Observatory), that storm hits the Earth. Accurate space
can provide stereoscopic images of 90 weather forecasts can give us the time
per cent of Sun’s surface to catch the to do things like divert planes, put
first signs of activity such as CMEs and satellites and communications hubs
solar flares. into ‘safe’ mode, and even identify and
disable power transformers that are
The Solar Dynamics Observatory most at risk.
(SDO), gives readings of the Sun’s

093

SPACE WEATHER

Solar tornadoes

Solar tornadoes

The story behind twisters on the Sun, a thousand Fiery atmosphere
times larger than their Earthling counterparts
In 2012, small-scale
A gigantic sphere of hydrogen plasma poles, as this is where magnetism is most magnetic tornadoes were
(ionised gas), our Sun is by far the most prominent. They exist on other stars as well as the discovered in the corona
dominant body in the Solar System and Sun, burn at over a million degrees Celsius (1.8 - where temperatures can
one of its most visually intense events is the solar million degrees Fahrenheit) and have swirling reach over a million degrees
tornado. These twisting magnetic fields are speeds of 10,000 kilometres (6,213 miles) per hour. - as well as the photosphere.
between 100 to 1,000 times larger than what we’re
used to on Earth and have been observed at a They appear in clusters and their main function Gas twisters
gigantic 70,000 kilometres (43,496 miles) tall. It is to heat the star’s outer atmosphere by moving
has been calculated that over 11,000 of these energy from the surface to the uppermost layer, The rotating magnetic
phenomena are on the Sun’s surface at any time the corona. They generate 100 to 300 watts per fields of the Sun
and they are believed to potentially be the source square metre (10.8 square feet) and are believed to generate the ionised
of heating for the outer reaches of the Sun and be the reason for the corona’s heat production, gas twisters, creating
could contribute to auroras on our planet. which has puzzled scientists and astronomers for its spiral shape.
Solar tornadoes differ from Earth-based generations. Observations from the Swedish 1m
twisters because they are comprised of a Solar Telescope in 2008 have increased our
magnetic field of plasma. They are more understanding of how nature heats magnetised
frequently spotted around the Sun’s equator and plasma and how the ‘chromospheric swirls’ we
can see are the result of the tornadoes.

The Swedish 1m Solar Telescope
discovered chromospheric
swirls, the visible sign of
magnetic tornadoes

Why is the corona so hot?

A curious anomaly of our nearest star into the corona by wave heating from
is the fact that the corona, an aura of the core. As the corona is dominated
plasma surrounding the star, is hotter by magnetic fields that are constantly
than many other areas of the Sun connecting and engaging with each
closer to its core. The corona can get other, a convection zone is created,
up to two million degrees Celsius (3.6 which releases high amounts of
million degrees Fahrenheit) while on energy and heat. Solar tornadoes are
the surface it is a measly 5,500 linked to the plasma’s astonishing heat
degrees Celsius (9,932 degrees levels as they contribute to coronal
Fahrenheit). Scientists and mass ejections (CME) and the solar
astronomers have long been winds in the Sun’s atmosphere. To
perplexed by this but some new discover more, NASA has planned a
theories might explain why. Recent mission known as the Solar Probe
notions reason that heat is injected Plus, which is pencilled in for 2018.

094

5TOP Solar flare Coronal mass ejection Sunspot Geomagnetic storm Solar prominence
FACTS
1 A massive magnetic energy 2 An eruption of solar wind 3 A relatively dark and cool area 4 Caused by CMEs and solar 5 Similar to a solar flare, solar
SUN PHENOMENA release on the Sun’s surface, a caused by magnetic of the photosphere, they have flares, radiation-charged prominences are loops of
solar flare shows sudden instabilities, CMEs can cause temperatures of around particles affect the Earth’s unstable plasma that extend
concentrated brightness and electrical problems to 3,500°C (6,330°F) and can magnetic field and cause from the surface to the
emits huge amounts of satellites and the Earth’s reach over 50,000km auroras in the North and corona, adding to the Sun’s
radiation into the Solar System. magnetosphere. (31,069mi) in diameter. South Polar regions. already vibrant appearance.

DID YOU KNOW? There are two types of solar tornado: giant and small-scale magnetic. Experts are unsure whether they are linked

Solar power Solar storm © SST/ISP; Wedemeyer-Böhm et al; NASA/SDO
chaser
This image illustrates a
giant solar tornado Dr Sven Wedemeyer-Böhm from the Institute
rather than a smaller
chromospheric swirl. of Theoretical Astrophysics explains more
The latter were only
discovered in 2008 and How similar are solar tornadoes to
had only been tornadoes on Earth?
observed in the Aside from the visible appearance, tornadoes
photosphere until 2012. on Earth and on the Sun are very different
phenomena. In both cases, the tornado funnel
Far-reaching is narrow at the bottom and widens with
height in the atmosphere. Particles inside
This twister extends all tornadoes are forced to move in spirals.
the way through the Sun’s Tornadoes on Earth occur as a result of
atmospheric layers from temperature and gas pressure differences and
the convection zone all strong shear winds. Solar tornadoes are
the way to the outer generated by rotating magnetic field
teaches of the corona. structures, which force the plasma, ie the
ionised gas, to move in spirals.
Spiralling out
of control How do solar tornadoes contribute to
auroras on Earth?
Like on Earth, solar It has been speculated that giant tornadoes
tornadoes have a may serve as a possible trigger of solar
narrow funnel at eruptions, where they build up a magnetic
the bottom, which field structure until it destabilises and erupts.
widens as it rises. As a consequence, ionised gas could get
ejected towards Earth, which would then
contribute to auroras. However, as of now,
there’s no direct connection confirmed.

Do you know about future planned missions
to investigate this phenomenon?
There are missions such as Solar Orbiter and
Solar-C, which may fly in foreseeable future.
There will be also some major progress with
ground-based observatories with the 4-m
Daniel K Inouye Solar Telescope (DKIST,
formerly the Advanced Technology Solar
Telescope, ATST), which is currently built on
Hawaii, and possibly the 4-m European Solar
Telescope (EST), which may be built in the
future. These new instruments will allow for
an even closer look at our Sun and will enable
us to answer the many open questions that
we still have about solar tornadoes.

What is the primary difference between
giant solar tornadoes and small-scale
magnetic tornadoes?
It is currently not clear if these are different
phenomena or not. Small-scale magnetic
tornadoes have only been observed from the
top so far, ie in the middle of the solar disk,
whereas giant tornadoes are seen more
towards the limb of the Sun, in other words:
from the side. In general, magnetic tornadoes
tend to have somewhat smaller diameters
than giant tornadoes but it is too early to draw
solid conclusions.

What is the primary difference between
giant solar tornadoes and small-scale
magnetic tornadoes?
There are still many questions concerning
solar tornadoes and we hope to address some
of the most important aspects during the next
three years in a project, which has just started
at the University of Oslo in collaboration with
international experts.

095

Extreme cosmic
temperatures Whatarethehottestandcoldest

temperatures that can be found in space?

Absolute zero

-273.15°C (-459.67°F)

The lowest temperature possible, zero degrees Kelvin
SPACE WEATHER
Elements Space tech Earth Solar System Milky Way Universe
Extreme temperatures
-272.2°C/-457.96°F 450 picokelvin
Fahrenheit
CelsiusLowest freezingColdest recorded
point temperature
096
Helium will remain liquid A team of scientists -250 -400 -240°C/-400°F -272°C/-458°F
right down to near from MIT cooled sodium -200 -328
absolute zero. gas to a fraction above Lunar craters Deep space
absolute zero. -200 refrigerator
-148 The Moon is cold
enough anyway, but The Boomerang nebula
-40 there are craters on its 5,000 light years from
0 surface in permanent Earth, is the coldest
shadow that never rise natural place in space.
above this temperature.

-150 Pluto’s icy heart

-40°C/-40°F -93.2°C/-135.8°F -100 From a distance of 450,000 kilometres (280,000
Equilibrium miles) away, New Horizons’ Long Range
Coldest place -50 Reconnaissance Imager (LORRI) took four photos
The point at which both on Earth -40 to create this composite colour image of Pluto,
the Celsius and revealing some curious details. The heart-shaped
Fahrenheit scales have This was measured in Tombaugh region (named after the astronomer who
the same value. eastern Antarctica by a discovered Pluto in 1930) is split into two lobes in this
NASA satellite, so is not image, and it’s thought that temperatures as low as -223 degrees
-38.83°C/-37.89°F an official Guinness Celsius (-369 degrees Fahrenheit) cause nitrogen to precipitate as
Mercury freezes world record. snow and flow from one side of the region to the next in massive
glaciers. The team at New Horizons mission control also think that
Your thermometer will this vast area acts as a kind of reservoir that feeds both its
be useless in the depths geological and atmospheric activity.
of an Antarctic winter.
-48°C/-54°F o
o
Coldest brown 0
0 dwarf star

Sub-stellar objects can
achieve surprisingly low
temperatures, including
this record-breaking
neighbour of ours that is
just 7.2 light years away.

32

70.7°C/159.3°F 50 100

Hottest place 100 212
on Earth 300
150 392
The Lut desert in Iran 1,000
achieved this record in 200 1,832
2005. It was measured 5,000
by satellite. 400
DID YOU KNOW? The highest recorded temperature on Earth was in the Lut desert in Iran, when the mercury hit 70.7°C2,200°C/3,992°F600
-1,538°C/-2,800°F 800 Unlike the Earth, there is no
097 Atmospheric solid surface on the Sun. It’s
Iron melts re-entry 1,000
2,000 completely gaseous
Under intense pressure, The heat shield on 3,000
such as at the Sun’s NASA’s new Orion 4,000 55,000,000°C/
core, iron will remain in capsule will protect its 5,000 99,000,032°F
a liquid state even at crew from blistering 6,000 Supernova gas
extreme temperatures. temperatures when 7,000
re-entering the The energy of a
Earth’s atmosphere. 10,000 5,500°C/ 10,000°F supernova can heat the
gas surrounding it to
3,093°C/5,600°F Surface of blistering temperatures.
the Sun
Rocket boosters 100 billion°C/
Hot enough to boil iron. 180 billion°F
The temperature within Core of a
the booster of NASA’s newly-formed
Space Launch System neutron star
– the most powerful
rocket booster ever built Massive stars that
– during tests. collapse sometimes
leave behind these
Heat of the Big Bang 8,000 100,000 24,000°C/ incredibly hot and
9,000 43,232°F dense remnants.
In the first few moments of its formation, the universe was 10,000 1 million
pretty toasty to say the least, with a temperature in excess 100,000 Core of Jupiter
of four trillion degrees Celsius (7.2 trillion degrees 18 million
Fahrenheit). The universe was so hot and dense that 1 million The immense pressure
protons and neutrons could not exist, but their constituent 10 million at Jupiter’s core from
elementary particles formed a quark-gluon plasma. This 100 million this massive planet,
so-called “quark soup” was 250,000 times hotter than the makes it a massive five
Sun’s core, but it cooled as the universe expanded. At 100 times hotter than that of
seconds after the Big Bang, the universe was at one billion degrees the Sun’s surface.
Celsius (1.8 billion degrees Fahrenheit), but it took 380,000 years before the
first hydrogen and helium atoms could form. 180 million 15,000,000°C/
27,000,000°F
1 billion
18 billion
5.5 trillion°C/ 1 trillion
9.9 trillion°F 1 quadrillion Core of the Sun
1 quintillion
Hottest recorded 1.8 trillion Not surprisingly, this is
temperature 1 sextillion the hottest place in the
1 septillion
This gong goes not to a Solar System, where
star or even a 1 octillion 1.8 quadrillion each of the fusion
supernova, but was
briefly generated by the reactions take place.
man-made particle
accelerator, the Large 1.8 quintillion
Hadron Collider.
1.8 sextillion

1.8 septillion

1.8 octillion

1 nonillion 1.8 nonillion

1 decillion 1.8 decillion

Planck temperature

©NASA 142,000,000,000,000,000,000,000,000,000,000°C (255,000,000,000,000,000,000,000,000,000,000°F)

The hottest (theoretical) temperature of matter achievable

SCIENCE
OF WEATHERThe causes and effects of our weather

112

100 Weirdest weather 118 Mammatus clouds 122 Cave weather
Understand the craziest How do they warn us of Learn about the microclimates
weather phenomena to hit incoming tornadoes? of caves
planet Earth
118 How is dew formed? 124 The ozone layer
110 How the seasons work How does this dampness form explained
on the ground? Get familiar with Earth’s much
Learn about what makes the at-risk ozone layer
Earth’s seasons so different to 119 What are Von Kármán
one another vortices? 125 Antarctica’s ozone hole
Witness the ever-evolving size
112 How the Arctic Ocean Understand the science of the ozone layer
freezes behind these mind-boggling
cloud formations 126 Cloud-spotting guide
What’s the science behind this Learn how to identify different
huge expanse of sea freezing? 120 How do waterfalls cloud types in the sky
freeze?
114 The carbon cycle Learn about what’s behind 127 Why are clouds white?
What happens to the air that moving water freezing? What makes the clouds above
we breathe? our heads appear white?

116 How does wind erosion 121 Why do we get red sky 127 Rain shadows
work? at night Find out all about the
phenomena of rain shadows
Witness the power of the Red sky at night, shepherd’s
wind to carve out dramatic delight. Is their truth in this 128 Why, and how, does it
landscapes old wives’ tale? rain?
What causes water to fall from
117 Atmospheric 121 What is wind-chill the sky?
temperature factor?
128 What are fog, mist and
Why does the air temperature How do we experience haze?
fluctuate with altitude? lower temperatures than are Learn to distinguish between
actually present? these three distinct and
117 Clouds that shine everyday weather events
at night 121 The smell of rain

How are noctilucent clouds Get to grips with what’s
formed high in the Earth’s behind he scent you witness
atmosphere? in the rain falls

098

SCIENCE OF WEATHER

122 121

129 Double rainbows 119
Are double rainbows just a
trick of the eye? 099

130 Why is snow white?
What makes snow appear
white to the naked eye?

131 What are lenticular
clouds?

Discover how cloud formations
can look out-of-this-world!

131 Aurora borealis
What are the reasons behind
the beautiful night sky lights

132 Nitrogen cycle
Find out how living organisms
exploit this abundant gas

134 Influencing cloud
formation
Explore the factors involved
with varying cloud types

135 Snow flakes
Understand the reasons
behind why these beautiful
crystals of ice form?

135 Weather symbols
Learn to read the weather
forecast with the intricate
symbols explained

SCIENCE OF WEATHER FIRE RAINBOW

Weirdest weather

VOLCANIC LIGHTNING

The science behind our planet’s most spectacular, dangerous
and downright bizarre weather phenomena

Weather key Cloud Wind Sun Heat Cold Rain Lightning Hail

FALLSTREAK HOLE ROLL CLOUDS DUST STORMS

Have you ever seen a swirling tornado of potential to be breathtaking, destructive and often the main catalyst for some of the world’s
fire, or heard a sand dune sing? even explosive. most extreme weather, spawning lightning, hail
Perhaps you’ve witnessed balls of and even tornadoes. However, wind, water and
lightning floating in the sky or even been caught The basis for most weather is wind, water and temperature can sometimes work in even more
in a downpour of frogs. Even if you haven’t, temperature. Thunderstorms are the perfect unusual ways to create bizarre weather
someone elsewhere in the world definitely has. example, as they involve all three at once. As the phenomena that scientists are still trying to
Although most of the weather we encounter Sun heats the Earth, moisture in the air rises up understand. Most weather, though, no matter
on a day-to-day basis isn’t particularly exciting, into the cooler regions of the atmosphere via a how rare and unusual, can be explained through
it can occasionally deliver some incredibly strong updraft. When it gets high enough, the relatively simple science, and over the next
strange surprises. From enormous hailstones moisture condenses into water droplets, forming few pages we will explore the fascinating
the size of tennis balls to towering clouds of dust clouds and eventually precipitation. Colder air processes that are behind some of our planet’s
that engulf entire cities, weather has the also sinks in strong downdrafts that create oddest examples.
powerful horizontal winds. Thunderstorms are

100