WIND SYSTEMS In Desert

• Most desert regions have been formed by movements of air masses over the planet.

• As the earth turns on its axis, it produces gigantic air swirls.
• Hot air rising over the equator flows northward and southward; the currents cool in the upper regions and descend as high-pressure areas in two subtropical zones.
• North and south of these zones are two more areas of ascending air and low pressure. Still farther north and south are the two polar regions of descending air.
• As air rises, it cools and loses its moisture. As it descends, it warms and picks up moisture, drying out the land.
• The downward movements of warm air masses over the earth have produced two belts of deserts, one along the tropic of Cancer, in the northern hemisphere, and the other along the tropic of Capricorn, in the southern hemisphere.
• Among the northern deserts are the Gobi in China, the deserts of southwestern North America, the Sahara in North Africa, and the Arabian and Iranian deserts in the Middle East.
• Along the southern belt lie Patagonia in Argentina, the Kalahari Desert of southern Africa, and the Great Victoria and Great Sandy deserts of Australia.