Climate, Arid and Semi-Arid Regions

Arid and semi–arid climates exist where more surface moisture is lost to evaporation than gained from precipitation. Arid and semi-arid climates cover 30 percent of earth's land surface, a larger land area than any other climate. These climates have low annual precipitation, abundant sunshine, and high evaporation rates. The difference between the maximum daytime and nighttime minimum temperatures is wide, ranging from 15–20 degrees C (27–36 degrees F). Low precipitation in arid and semi-arid climates is influenced by the presence of semi-permanent, subtropical high-pressure areas located across the globe around 30 degrees latitude. These highpressure zones are large areas of descending air aloft, limiting cloud development and precipitation.

Subtropical arid climates, such as the Sonoran Desert, Rub al-Khali, Sahara, and the Australian Outback, are located at ...