Climatology of Tropical System Rainfall in the Eastern Corn Belt

Abstract

his study examines the frequency of daily rainfall totals greater than 2.54 cm (1 in.) averaged within a climate division (CD) associated with tropical systems that moved through the U.S. eastern Corn Belt region during the growing season. These occurrences are defined as ?events.? From 1913 to 2012, the tracks of 60 tropical systems moved over a study area that included 24 CDs?9 in Illinois, 9 in Indiana, and 6 in western Ohio. Of those 60 tropical systems, 37 were associated with events. Event risk varied through the growing season ranging from 3 events in June to 21 events in September. Decadal analysis showed an increase in the frequency of tropical systems and events during the last decade of the study (2003?12). Tropical systems were infrequent, and the timing of rainfall associated with the majority of events (i.e., September) was too late to impact corn and soybean development or yield in this region. Events had some impact on current and subsequent CD average soil moisture conditions; however, only 8 of the 37 events produced dramatic improvements in Palmer drought severity index (PDSI) values from categorical moderate to severe drought levels to near-normal conditions in the eastern Corn Belt. Those CDs that experienced a September or October event were associated with significantly higher PDSI values (+1.34) prior to the following summer than those that did not experience an event (+0.54).