WHAT IF...
What if our weather
systems reversed?
What would the weather be like if weather systems
suddenly came from the east instead of the west?
METEOROLOGY North America,
Europe and North Africa are located in
the westerlies wind belt, where the
climate is determined by westerlies
and western ocean currents. If the
system’s direction changed, the
climate would be markedly altered.
During most of the year, westerlies
carry the warm, moist air inland. So
the climate is mild in summer and in
winter, while frequent precipitation
makes the soil fertile.
Towards the east, the air is dry
and temperatures more extreme. If
easterlies replaced the Gulf Stream and
westerlies, North European winters
would become up to 20 degrees colder,
while the summers would be hot and
dry, as the air would no longer be
supplied with evaporated ocean water.
Australia’s weather is also affected
by strong westerly winds that blow
almost continuously in the mid-to high
latitudes of the southern hemisphere.
Storms and cold fronts tend to move
from west to east, bringing rainfall to
southern and eastern Australia.
Our weather is also affected by the
north-to-south shift in these westerlies,
known as the SAM, or Southern
Annular Mode. A positive SAM occurs
when the westerlies contract towards
the pole, increasing the chance of rain
in the east, but decreasing it in the
west and south during winter. When
the westerlies expand towards
Australia it is called a negative SAM,
reversing the above results in winter,
but reducing rainfall across the whole
south-east when occurring in summer.If the weather systems
changed direction from west to
east, winters would be much
colder and summers drier.
Westerlies control
heat and precipitation
Westerlies are key to Europe's
mild, moist climate. Easterlies
would mean a dry climate with
major temperature differences.Westerlies in Europe:
Westerlies carry warm moist air
produced by the Gulf Stream inland,
making the climate mild and fertile.Easterlies in Europe:
Dry air from the continent flows
across Europe. Winters become
cold, and summers are hot and dry.CLA
US
LUN
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HU
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RST
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Wind direction
Wind direction
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