This is a grant under a Climate Variability and Predictability (CLIVAR) Program pilot project called DRICOMP, for the Drought in Coupled Models Project, which focuses on making initial explorations into the mechanisms of drought as they are represented in the output of global climate models and on attempting to assess the reliability of these models in simulating drought.
Possible causes for the geographic preference and remote forcing of warm-season droughts in the U.S. Central Plains have been suggested: . The large-scale flow pattern of Central Plains drought is characterized by a ridge in the western United States and a trough in the eastern United States. This pattern resembles the spring-to-summer flow regime change across North America, which is accompanied by a drastic June-July decrease in the Central Plains rainfall maximum. This favorable continental-scale environment for drought is established by the global spring-fall annual and the March-June semiannual modes which are much weaker than the winter-summer annual mode. . Without any special interannual forcing, the atmospheric circulation should only undergo a regular seasonal variation in response to the seasonal cycle of solar heating. Thus, to identify possible interannual forcing and the atmospheric response to this forcing, the regular seasonal cycle should be removed. Applying this approach, a cross-Pacific short-wave train emanating from an interannual rainfall anomaly center over the western subtropical Pacific appears to couple with the Central Plains drought flow pattern across the U.S. continent.
Using these findings, two avenues of research will be explored: 1) to attempt an evaluation of whether the seasonal-cycle modes forming environments favorable for Central Plains droughts are well simulated by global and regional climate models, and 2) to make an initial test of whether simulated Central Plains droughts are stimulated by the western subtropical forcing. The goal of the study is to propose new mechanisms leading to Central Plains droughts.
Broader impacts of this work lie in its potential for providing enhanced predictability of drought in the Great Plains.
