Geography studies with Mr Homela

Location of Hot Deserts.
The largest arid and semi-arid deserts occur
between latitudes 15° and 30° North and South of
the equator.
Most of these deserts are located on the western
sides of the continental masses on which they lie.
They occur within the Trade wind belt where the
winds are off-shore.
Off-shore winds are those winds that blow from the
shore towards the ocean.
These winds (Trade winds) tend to be dry after
loosing their moisture as they journey across the
eastern side of contents.
Although west coasts have on-shore winds (winds
from the ocean towards the land) blowing towards
them, they rarely bring rain.
This is because the onshore winds meet with cold
currents that blow parallel to coast lines (e.g. the
Cold Benguela current in the case of the Kalahari
and the Cold Angola current in the case of the
Namib desert) this causes the moisture within the
on-shore winds to condense and form mist, fog and
light rain before the winds reach the coast.
Most of the winds that blow across deserts are
land winds which are dry/contain little moisture and
therefore do not result in any form of precipitation.
Some deserts as the Arizona desert are far from
oceans, moisture from oceans is exhausted in the
form of rainfall in other areas before it reaches
these deserts since they are further in the interior.
Some deserts such as the Gobi Desert, are located
in rain shadow areas because they are in
depressions or basins.
Since they are on the leeward side of mountains
where warm dry air is sinking they tend to receive
little to no rainfall.
In addition to this the relative humidity of the air
mass falls resulting in high evapotranspiration rates
thus exacerbating the aridity of deserts while
increasing their temperature.
The Kalahari and Sahara deserts are also located on
the rain shadow side of major mountains.
In Zimbabwe areas like Save valley and major parts
of Matabeleland are hot and receive very little
rainfall, droughts are frequent and may eventually
become deserts.
Some deserts are located in the sub-tropical high
pressure zone 30° North and South of the equator
which means winds tend to blow from these areas
and dry warm air is sinking creating permanent
High pressure belts.
In some areas as the Patagonian Desert cool off-
shore currents prevent local on-shore winds from
bringing in rain.
Most Hot Deserts are increasing in area in a
process called desertification.
Human action sometimes contribute to
desertification so in some ways deserts are a man
made feature.
Climate change has also resulted in changes in
local rainfall patterns with increased incidence of
droughts in places like Somalia where rainfall might
not fall for years on end.
This topic will be looked at separately later.