Chapter 4 - Moisture deficit and surplus in the conterminous United States for three time windows: 2016, 2014-2016, and 2012-2016This article is part of a larger document. View the larger document here.
Droughts affect most forested ecosystems of the United States, but they vary widely in frequency and intensity (Hanson and
Weltzin 2000). Most western U.S. forests experience annual seasonal droughts, with the seasonality determined by broadscale
atmospheric circulation patterns and topography. For example, forests along the Pacific Coast usually experience dry summers and wet winters, while forests in Arizona and western New Mexico rely in part on rainfallreceived during a summer monsoon season (Adams and Comrie 1997, Hanson and Weltzin 2000). In contrast, eastern U.S. forests typically exhibit one of two predominant drought patterns: random (i.e., occurring at any time of year) occasional droughts, as observed in the Appalachian Mountains and the Northeast, or frequent late-summer droughts, as commonly seen in the southeastern Coastal Plain and the eastern portion of the Great Plains (Hanson and Weltzin 2000).