(press release). This article from 2000 describes how scientists use data from satellites and rain gauges along with tree-rings and lakebed sediments to understand and predict drought in North America.">


back Physical Processes that Cause Drought


Soil moisture plays an important role in preventing or prolonging summer droughts. When the ground is wet, water evaporates as the day warms up. The warm, moist air rises until it encounters colder air high above the Earth's surface, leading to afternoon rainshowers. The water remains in the ground through the cool night, and the cycle repeats the next day. (Animation courtesy Susan Byrne, NASA GSFC)