Moisture recycling over the central United States diagnosed from the North American Regional Reanalysis

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Monday, 18 January 2010: 12:00 AM
B304 (GWCC)
Christopher J. Anderson, Iowa State University, Ames, IA; and R. W. Arritt

We have diagnosed the regional atmospheric water cycle over the north-central U.S. using data from the North American Regional Reanalysis. Our focus is on the recycling ratio, which indicates the fraction of rainfall that originates from local evaporation over a region. The recycling ratio follows the basic approach of Brubaker et al. (1993) and we include a method to account for the effect of the reanalysis increment following Schubert and Chang (1996) . The methodology was applied to the warm-season months (March-September) of 1979-2002 over the north-central U.S. Corn Belt extending approximately from Iowa through Indiana. Results show that peak recycling ratio occurs progressively later in the warm season from west to east in the Corn Belt with maximum value in May in the western part of the region and a broad maximum from June through August in Indiana. The recycling ratio also varies considerably from year to year; interannual variability is greatest in April and May and tends to be small in September. Anomalies such as springtime drought can affect the moisture budget later in the year after the anomaly has ended, most likely through its effect on the growth and development of transpiring vegetation.