The Dry Climate
These climates are characterized by the fact that precipitation is less than potential evapotranspiration. Desert areas, situated along the west coasts of continents at tropical or near-tropical locations, are characterized by cooler temperatures than encountered elsewhere at comparable latitudes (due to the nearby presence of cold ocean currents) and frequent fog and low clouds, despite the fact that these places rank among the driest on earth in terms of actual precipitation received. In this climate, summers are hot to very hot and it seldom rains. Winter days may be cool or warm, and winter nights can be very cold. The air is dry, there is little cloud; sunshine is intense and glare can be a problem. There is a big temperature difference between day and night.
Desert Biome - Dry Tropical Climate (BW)
These desert climates are found in low-latitude deserts approximately between 18° to 28° in both hemispheres. these latitude belts are centered on the tropics of Cancer and Capricorn, which lie just north and south of the equator. They coincide with the edge of the equatorial subtropical high pressure belt and trade winds. Winds are light, which allows for the evaporation of moisture in the intense heat. They generally flow downward so the area is seldom penetrated by air masses that produce rain. This makes for a very dry heat. The dry arid desert is a true desert climate, and covers 12 % of the Earth's land surface.
- Temperature Range: 16° C
- Annual Precipitation: 0.25 cm (0.1 in). All months less than 0.25 cm (0.1 in).
- Latitude Range: 15° - 25° N and S.
- Global Range: southwestern United States and northern Mexico; Argentina; north Africa; south Africa; central part of Australia.
Steppe - Dry Midlatitude Climate (BS)
Characterized by grasslands, this is a semiarid climate. It can be found between the desert climate (BW) and more humid climates of the A, C, and D groups. If it received less rain, the steppe would be classified as an arid desert. With more rain, it would be classified as a tallgrass prairie.
This dry climate exists in the interior regions of the North American and Eurasian continents. Moist ocean air masses are blocked by mountain ranges to the west and south. These mountain ranges also trap polar air in winter, making winters very cold. Summers are warm to hot.
- Temperature Range: 24° C (43° F).
- Annual Precipitation: less than 10 cm (4 in) in the driest regions to 50 cm (20 in) in the moister steppes.
- Latitude Range: 35° - 55° N.
- Global Range: Western North America (Great Basin, Columbia Plateau, Great Plains); Eurasian interior, from steppes of eastern Europe to the Gobi Desert and North China.