Hot Arid and Semi-arid Environments. CLASSIFICATION AND DISTRIBUTION OF HOT ARID AND SEMI ARID ZONES. Definitions. Simple one What is a desert (arid area)? <250mm precipitation per year (Semi arid area = 250 – 500 mm per year) More advanced……. WHAT IS ARIDITY?.
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CLASSIFICATION AND DISTRIBUTION OF HOT ARID AND SEMI ARID ZONES
What is a desert (arid area)?
(Semi arid area = 250 – 500 mm per year)
Ratio of average precipitation (P) to potential evapotranspiration (PET*) = aridity index
Arid areas: <0.20
Semi-arid areas 0.20 -0.50
*See page 134 for def of pet
Hot dry with winter dry season
e.g. sub Sahara
Sahara and Middle East
Not studied for A level
Five main areas of Hot arid regions
Each with various sub-divisions
based on Alice Springs fig 4.2
Other points to note
Defining factor of areas BUT
This sinking air is warming as it descends due to compression, making the atmosphere cloud free – causing a permanent high pressure air (sub-tropical high) and little likelihood of rain
I.e where the world ‘s arid regions are
Offshore winds Trade winds to the equator at ground level called the trade winds