How does a drought happen?

Answer 1

A drought is an extended period of significantly below average precipitation in a region. There are several reasons why they happen.

Severe droughts occur commonly in the interior and towards the western coast of continents, particularly Africa and Australia. However, they can occur anywhere, and with different levels of severity.

Drought is an abnormally long period of dry weather because there is a severe lack of water in an environment over an extended period of time. For a drought to happen, it means that rainfall has fallen below the average necessary to water crops and/or livestock, and to refill dams for months at a time. When moisture near the ground rises into the colder areas of the upper atmosphere rain clouds form. High pressure in the atmosphere causes air to rise instead of falling, resulting in dry, sunny weather. When high pressure cannot be displaced by low-pressure for an extended period of time, the result is drought.

Lack of rain may be a result of the El Nino phenomenon, which brings dry conditions to some parts of the world for sometimes as long as several years at a time. This is why the southern continents of Africa and Australia are particularly prone.

Desertification is a vicious cycle which increases drought-like conditions, and makes it increasingly difficult for the land to recover. Desertification may occur as a result of man's intervention in the environment, particularly activities such as deforestation and cutting down trees, over-grazing of stock animals, or farming unsuitable crops for a region (e.g. rice, which has to have large amounts of water pumped to it).

Some recent droughts are believed to have happened because of global warming.