Droughts
DroughtsDrought, condition of abnormally dry weather within a geographic region where some rain might usually be expected. A drought is thus quite different from a dry climate which designates a region that is normally, or at least seasonally, dry.
Athough the quantity of the worlds freshwater resourses is more than adeguate to meet human needs, but uneven distribution from place to place can result in serious droughts.
The word drought is applied to a time where an unusual shortage of rain causes a serious hydrological imbalance: Water-supply reservoirs are empty, wells dry up, and crop damage ensues. The severity of the drought is determened by the degree of moisture deficiency, its lengh, and the size of the area affected. If the drought is short, it is known as a dry spell, or partial drought. A partial drought is usually defined as more than 14 days without a notable amount of precipitation, onthe other hand a drought may last for years.
Droughts tend to be more severe in some areas than in others. Catastrophic droughts generally occur at latitudes of about 15�-20� and in areas bordering the permanently arid regions of the world. Lands that are permanent arid is a characteristic of those areas where warm, tropical air masses, in descending to earth, become hotter and drier. When a poleward shift in the west ocurrs, the high-pressure, anticyclonic conditions of the permanently arid regions hit each other on areas that are normally used to seasonally wet...
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