Wind Causes California Droughts

October 12, 2016

Droughts in California are mainly controlled by wind, not by the amount of evaporated moisture in the air, new research has found.

The findings were published in Geophysical Research Letters, a journal of the American Geophysical Union, on June 30, 2016. The research increases the understanding of how the water cycle is related to extreme events and could eventually help in predicting droughts and floods, said lead author Jiangfeng Wei, a research scientist in the Jackson School’s Department of Geological Sciences.

The researchers analyzed 30-year data sets that recorded precipitation, ocean evaporation, surface wind speed and atmospheric pressure on and near the west coast of the United States. These are all factors that influence the water cycle in California.

Their analysis showed that although moisture evaporated from the Pacific Ocean is the major source for California precipitation, the amount of water evaporated did not strongly influence precipitation in California, except in the cases of very heavy flooding. Instead, the researchers found that disturbances in atmospheric circulation, the large-scale movement of air, have the most effect on drought because they can impact factors that will cause it to rain more or less.

The study co-authors are Qinjian Jin, a postdoctoral researcher at the Massachusetts Institute of Technology who earned his Ph.D. at the Jackson School; Zong-Liang Yang, a professor in the Jackson
School’s Department of Geological Sciences; and Paul Dirmeyer, a professor at George Mason University.