Abstract Author: Martin Hoerling, Jon Eischeid and Xiao-Wei Quan
Abstract Title: Early Warning Indicators for U.S. Drought
Abstract: To what extent is severe sustained drought foreshadowed by global sea surface temperature? Was the Dust Bowl potentially predictable, and is there early warning capability for the next Dust Bowl-like drought? Which patterns of severe sustained U.S. drought have the greatest prospects for early warning, and what are their oceanic predictors? Is there early warning of U.S. drought severity for the upcoming decade?
We present analyses of the relationship between leading patterns of U.S. drought and global SSTs during 1895-present. We include data from atmospheric models forced by observed SSTs and coupled ocean-atmosphere models forced by observed greeenhouse gas, aerosol, and solar variability. The leading pattern of observed and simulated U.S drought (diagnosed using a Palmer Drought index) is characterized by a nationwide pattern of drying, having maximum intensity in the central and northern Great Plains. Our diagnosis finds little evidence that such a drought has early warning capability based on SSTs alone….neither empirical analyses, atmospheric model simulations, nor coupled model simulations indicate that the Dust-Bowl like drought pattern has strong SST precursors. In contrast, the ENSO phenomena is shown to provide a more viable early warning for U.S. drought particularly over the southern U.S.. As concerns the next decade, we highlight the divergence between observed and greenhouse gas forced simulations of tropical SST change, and discuss implications for future U.S. drought.