Spatial and temporal patterns of drought in the Continental U.S. during the past century

This study investigates the spatial and temporal patterns of multiple drought characteristics (duration, severity, and intensity) under different return periods during 1900–2012 in the Continental U.S. (CONUS). We find two significant patterns: Pattern I shows persistent droughts in western and eastern U.S. and the Great Plains, which experienced large variations in the drought characteristics over long time; Pattern II shows transient droughts in the interior of CONUS, which experienced short-term variations in drought characteristics. Trend analysis shows that duration, severity, and intensity of droughts under the various return periods are increasing in most of the Pattern I regions. Moreover, spatial distributions of duration, severity, and intensity of more frequent and less severe drought events are found to be different from those of less frequent and more severe droughts in the same time period; trends in these drought characteristics at long and short return periods are different at some locations, showing the different trends of extreme and mild droughts.