Weather and Climate: Tropical wet and dry region

Describe the Sahel
A region of west africa that is a semi-arid expanse of grassland, shrubs, and throny trees lying just south of the sahara between the latitudes of 14 and 18N.
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what countries is the sahel comprised of
portions of 10 countries, including Algeria, Niger, and Nigeria
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what is the temperature in the Sahel
Monthly mean temperatures range from 18-36C due to proximity to the equator and low angle of insolation incidence.
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What is the precipitation in the sahel?
Rainfall varies: 100-200mm in the north and 400-800mm in the south.Mean figures tend to be misleading as rainfall pattern is characterised by high seasonality and variability.
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Rainfed cropping accounts for __% of the cultivated area in the Sahel
Rainfed cropping accounts for 95% of the cultivated area in the Sahel
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What has been the trigger mechanism for famine in the sahel?
persistent lack of rainfall. The continuing drought has developed gradually since 1968 and rainfall remained low in the 1980's
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Describe the wet season
There is a hot, wet season from june-sept with temp above 26C and heavy convectional rain. occurs when the ITCZ moves polewards with overhead sun, creating low pressure to produce strong rainfall.
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Describe the dry season
The rest of the year there is a warm dry season when high pressure dominates. Offshore trade winds blow across the area. they are steady and strong. created as air is pulled toward the low pressure of the ITCZ
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Water must be __C and __m deep to allow for enough evaporation for a tropical revolving storm to take place.
Water must be 27C and 70m deep to allow for enough evaporation for a tropical revolving storm to take place.
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What is a tropical revolving storm?
A low pressure system spinning anticlockwise in the northern hemisphere and always moving west due to trade winds.
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how big are tropical revolving storms?
200-700km in widrh
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wind speed of tropical revolving storm
300kmph
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At what latitudes do tropical revolving storms occur?
Between 5-20N and S of the equator. there is no Coriolis force at 0 so there cannot be any tropical revolving storms here.
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what powers tropical revolving storms?
The latent heat of evaporation as energy is released from the state change of the ocean from liquid to gas
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How are tropical revolving storms different to mid-latitude depressions?
Both are depressions, but a tropical revolving storm is formed by evaporation and insolation rather than two air masses meeting as in the mid-latitudes.
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Describe the pressure gradient of a tropical revolving storm
The eye has low pressure as the point of most evaporation and is surrounded by relatively high pressure. this creates a high pressure gradient accounting for the high windspeeds.
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where is most and least affected by tropical revolving storms
South east asia is most affected with 26 per year, India is least affected with only 2
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Card 2

Front

what countries is the sahel comprised of

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portions of 10 countries, including Algeria, Niger, and Nigeria

Card 3

Front

what is the temperature in the Sahel

Back

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Card 4

Front

What is the precipitation in the sahel?

Back

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Card 5

Front

Rainfed cropping accounts for __% of the cultivated area in the Sahel

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