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What Causes Drought?


What Causes Drought?

For areas that rely on regular rainfall to nourish vegetation, animals and a large human population, drought can be devastating, but in other parts of the world, hot, dry weather is a normal everyday occurrence.

These arid climate conditions are caused by circulatory patterns of air in the Earth’s atmosphere, known as Hadley cells.
In this weather system, intense exposure to sunlight at the equator causes warm, moist air to rise. As the air rises, it cools again, forming a low-pressure system that results in regular thunderstorms across the region. Above these storms, the jet stream – a current that flows through Earth’s upper atmosphere – carries the air towards higher latitudes until it eventually descends over the tropics to the north and south of the equator. As it falls, it creates a high-pressure system that is responsible for the arid conditions of the Sahara and other deserts that populate this particular region.

Slight changes in this movement of air can result in unusual – and sometimes catastrophic – weather activity, such as flooding and drought. For example, if the air that normally descends over the tropics in the Northern Hemisphere is carried further north by the jet stream, it can bring extended periods of high pressure to Europe. This can cause precipitation levels to fall below the expected average for the region, resulting in a period of non-seasonal drought.
Despite using advanced weather prediction models, experts are still only able to forecast drought when it is less than a month away, making it hard for countries to be prepared. If not, the impact can be extremely severe.

What Causes Drought?