Projecting Changes in Extreme Precipitation in the Midwestern United States Using North American Regional Climate Change Assessment Program (NARCCAP) Regional Climate Models

Abstract

Based on the physics of global circulation, many expect an enhanced greenhouse effect to lead to a more active hydrological cycle with more precipitation on average (Hennessy et al. 1997). This expected increase has been found in observations (Zhang et al. 2007) and has also been suggested by climate models, although these models are not consistent with respect to the spatial and temporal variability about this change. An increase in mean precipitation depth, assuming no change in the shape of the frequency distribution, would imply an increased frequency of heavy-precipitation events. However, some studies (Hennessy et al. 1997, Allen and Soden, 2008) also suggest the increase in these extreme events could be disproportionate to the change in the mean, with a greater fraction of the total precipitation being delivered by such heavy precipitation events. Such a shift towards heavy events is a common conclusion of climate models (Cubasch et al. 2001, Meehl et al. 2007) as well as analyses of observed rainfall data at the continental scale (Easterling 2000, Kunkel 2003, Groisman 2005, Min et al. 2011). However, there is great spatial variation of this average pattern. This study aims to establish likely future projections for how extreme precipitation frequency and magnitude could change in the Midwestern region of the United States, and investigate the spatial variation of such changes within the area.