Warm Season Land Surface — Climate Interactions in the United States Midwest from Mesoscale Observations

Abstract

The United States Midwest over the last two decades has experienced marked warm season climate anomalies, including droughts and major floods. While the development of these extreme events can usually be traced to anomalies in atmospheric circulation, and may include teleconnections, studies based on model simulations have shown that land surface forcing may be partly responsible for the persistence of these climate anomalies. This study evaluates the presence and strength of long-term land surface-climate interactions in the U.S. Midwest. We do this via an analysis of the cross-seasonal (spring and summer) associations between temperature and moisture (Palmer Drought Severity Index-PDSI, Crop Moisture-Z Index, and precipitation) anomalies. Direct and lag correlations for the 1895-1995 and 1948-1995 periods show that warm and dry summers tend to follow warm spring seasons. These results imply that springtime precipitation anomalies may help to determine the temperature regime of the following summer, possibly via the moisture content of the upper soil. We also show that broad land cover types tend to modulate summer climate anomalies in the U. S. Midwest.