Climatology-Regional Climatology Chapter 28
HEIGHT OF THE TROPOPAUSE AND 0°C ISOTHERM
JANUARY
Tropopause 47 000 ft
0°C Isotherm 14 000 ft
JULY
Tropopause 45 000 ft
0°C Isotherm 10 000 ft
SURFACE WINDS
In both hemispheres, the surface winds diverge from the sub-tropical zones of high pressure to
form the trade winds.
Circulation causes the mid-latitude westerlies to merge with the “Brave West Wind” in the
southern hemisphere to form the Roaring Forties. These winds blow consistently in the southern
hemisphere because there is no land mass to interrupt their flow.
JANUARY
In the Pacific the monsoon blows from a northerly direction on the eastern seaboard of Asia and
the island archipelagos. The south east trade winds and the southern coast affect Australia,
especially Queensland, by south westerly winds.
JULY
The west Pacific basin and Japan are under the influence of the south west monsoon. South
Australia has mainly westerly winds associated with the travelling depressions of the mid-
latitudes.
SIGNIFICANT WEATHER
JANUARY
The northerly monsoon of the west Pacific is generally dry. However, after its long sea track it
acquires moisture before arriving over the island archipelagos of east and south east Asia and
Australia where it combines with the north east trades. Typical trade wind weather is CU with
accompanying showers.
The ITCZ has CU and CB with TS in varying intensity. Tropical revolving storms, cyclones, are
found off Queensland and Fiji. Off the Northern Territories these storms are termed the Willy
Willys and occur from January to March.
Note: The real Willy Willys are dust storms in central Australia.
South Australia occasionally experiences the Brickfielder, a hot dusty wind which originates in
the central Australian desert. These winds bring poor visibility in haze and occur during the
summer months of the southern hemisphere.
Near Sydney a strong southerly wind, Southerly Buster, brings dense CU cloud and heavy rain.
This usually signifies the passage of a vigorous cold front and is accompanied by a noticeable
drop in temperature.
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In the north Pacific the families of travelling depressions are a feature of the temperate latitudes.
JULY
The west Pacific basin is influenced by the moist southerly monsoon. For Japan, the wettest
period is in June and July where the skies are overcast and produce continuous rain.
Typhoons occur from July to October from the south Philippines to Japan. On the opposite side of
the ocean the moist winds over the cold Californian current create advection fog mainly in the
vicinity of San Francisco. In the South Pacific, at the temperate latitudes, travelling depressions
march along the South Australian coast.
SOUTH AMERICA AND THE CARIBBEAN
TEMPERATURE DISTRIBUTION
JANUARY
The east west alignment of the isotherms is considerably distorted by the South American land
mass due to the sun being in the southern hemisphere during the summer months.
In the more southerly latitudes of the continent there is a considerable temperature gradient on
the west coast. It is here that the Humboldt Current travels north along the coast.
JULY
There is little variation in the temperature distribution from that in January. The temperature
gradient in the higher latitudes is shallower due to the cooling of the land in the southern
hemisphere winter and the sea being approximately the same temperature.
PRESSURE DISTRIBUTION
Because there is little variation in temperature through the year the pressure variation is minimal.
The equator effectively passes through the centre of the area.
JANUARY
The ITCZ advances south into the Amazonian rain forests of Brazil.
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Climatology-Regional Climatology Chapter 28
JULY
The ITCZ is aligned east west across Columbia and Venezuela.
UPPER WINDS
These winds are mainly equatorial easterlies flanked on either side by westerlies.
JANUARY
The zone of easterlies is south of the equator.
JULY
The easterlies lie mainly above the equator.
HEIGHT OF THE TROPOPAUSE AND 0°C ISOTHERM
JANUARY
Caribbean 54 000 ft
Tropopause 14 000 ft
0°C Isotherm
Central Brazil 52 000 ft
Tropopause 16 000 ft
0°C Isotherm
JULY 52 000 ft
16 000 ft
Caribbean
Tropopause
0°C Isotherm
Central Brazil 51 000 ft
14 000 ft
Tropopause
0°C Isotherm
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SURFACE WINDS
JANUARY
The north east trade winds circulating around the Bermuda high affect the Caribbean and the
northern part of South America. These winds blow behind the ITCZ deep into the Amazonian rain
forest. The south east trade winds touch the coast of north Brazil.
The west side of the continent has a cold water current and offshore winds are a prominent
feature of the sub-tropical latitudes. In the temperate latitudes westerly winds predominate.
JULY
The north east trade winds affect the Caribbean and only the very northern part of South
America. The south east trade winds move further north along the east coast. At mid-latitudes,
further south, the temperate westerlies are still a persistent feature.
SIGNIFICANT WEATHER
The ITCZ lies across the South American continent throughout the year. The typical weather
consists of CU and CB with the attendant TS.
In the Caribbean the typical trade winds prevail but hurricanes can occur between June and
October.
To the south of the continent temperate latitude travelling depressions occur with the typical
weather associated. A typical wind that blows with the fronts associated with the depressions is
the Pampero.
The Zonda of northwest Argentina is a Foehn wind which blows down the eastern slopes of the
Andes.
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