Scale Interaction Mechanisms in Midwest Droughts and Floods

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9627890 Arritt The goal of this project is to understand and estimate quantitatively the linkage between large-scale atmospheric circulation anomalies and the atmospheric component of the regional hydrological cycle associated with Midwestern summertime floods and droughts. Between 1979 and the present, there were four major flood and three major drought years. For those year, the principal investigators will carry out (1) diagnostic analyses of global circulation patterns in National Centers for Environmental Prediction (NCEP) global reanalyses, supplemented by rain-gauge precipitation data for the midwestern region and (2) simulations with NCAR's MM5 regional model, run in climate mode and driven by large-scale forcing from the NCEP analyses, focused on exploring regional water vapor fluxes and the mechanisms relating them to the large-scale forcing. Special attention will be given to the role of the southerly low-level jet in defining the water vapor transport and flux divergence. For one of the years of interest, an important additional source of high resolution data will come from specially processed wind profiler data. These studies are critical to understanding the hydrological cycle and will contribute to the goals of the Global Energy and Water Experiment (GEWEX) of the World Climate Research Program. This project is supported under NSF's Water and Energy: Atmospheric, Vegetative, and Earth Interactions (WEAVE) Initiative of the Global Change Research Program. ***