Decadal variability in the frequency of fall precipitation over the United States

Abstract

We examined decadal variability in fall daily precipitation across the United States over the period 1948 to 2004. By analyzing daily precipitation, we are able to decompose the interannual variability in fall total precipitation into the contributions of variations in the frequency of precipitation and variations in the mean rain day precipitation. Principal components analysis suggests that coherent variations in fall precipitation total across the central United States exhibit strong decadal variability that is due to coherent decadal variations in the frequency of precipitation. A wavelet analysis of regionally averaged total, frequency, and mean rain day precipitation and a series of synthetic experiments that allowed the shape and location of the distribution to change confirmed that the source of the observed decadal variability is the frequency of events rather than changes in the distribution of daily precipitation. Copyright 2007 by the American Geophysical Union.