Everything about Arid totally explained
In general terms, the
climate of a local or region is said to be
arid when it's characterized by a severe lack of available
water, to the extent of hindering or even preventing the
growth and
development of
plant and
animal life. As a result, environments subject to arid climates tend to lack vegetation and are called
xeric or
desertic. Juba, South Sudan is an Arid land.
Concepts
The expression 'available water' refers to water in the soil in excess to the
wilting point. The air over a hot desert may actually contain substantial amounts of
water vapor but that water may not be generally accessible to plants, except for very specialized organisms (such as some species of
lichen). 'Lack of water' refers to use by plants. The water that's actually present in the environment may be sufficient for some species or usages (such as
climax vegetation), and grossly insufficient for others.
Aridity, the characteristic nature of arid climates, may thus depend on the
use of the land. Regards to the presence of life, what is more important than the degree of rainfall is the fraction of
precipitation that isn't quickly lost through
evaporation or
runoff. Attempts to quantitatively describe the degree of aridity of a place has often led to the development of
aridity indexes. There is no universal agreement on the precise boundaries between classes such as 'hyper-arid', 'arid', '
semi-arid', etc.
Geographical distribution
If different classification schemes and maps differ in their details, there's a general agreement about the fact that large areas of the Earth are considered arid. These include the hot deserts located broadly in sub-tropical regions, where the accumulation of water is largely prevented by either low precipitations, or high evaporation, or both, as well as cold deserts near the poles, where water may be permanently locked in solid forms (snow and ice). Other arid regions include areas located in the
rain shadows of major mountain ranges or along coastal regions affected by significant upwelling (such as the
Atacama Desert).
Change over time
The distribution of aridity observed at any one point in time is largely the result of the general circulation of the
atmosphere. The latter does change significantly over time through
climate change. In addition, changes in land use can result in greater demands on soil water and induce a higher degree of aridity. See
aridification.
Further Information
Get more info on 'Arid'.
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