摘要：We investigate ensemble-mean ('consensus') values of resolution-weighted CMIP5 multi-model simulations of 1976–2005 summer regional hydroclimates, and of their projected 2070–2099 changes under three progressively more severe representative concentration pathways greenhouse scenarios. Uncertainties in these consensus values are estimated from the cross-ensemble scatter. We analyze differences among 30 year present-day and future consensus summer hydroclimates that are averaged over three disparate regions of the United States: the semi-arid Southern Great Plains, the arid Southwest, and the humid Southeast. Our study considers the impact of several scenarios of greenhouse forcing on the regional averages of both single hydroclimatic variables and on ratios of variables which are indicative of continental drying, as well as the partitioning of surface moisture or available energy into their respective subcomponents. In all three study regions, there is a projected robust increase in surface temperature as the severity of the greenhouse scenario increases; but the regional-average hydroclimatic changes are comparatively uncertain, and often are not proportional to the change in surface warming. There is, however, a projected robust increase in continental drying that is manifested by several complementary measures, but that differs in magnitude by region. The prospect of future continental aridification should be viewed with some caution, however, since it may be a result of various shortcomings in current-generation climate models or in the specified greenhouse scenarios.
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