Predicting Summer Dryness Under a Warmer Climate: Modeling Land Surface Processes in the Midwestern United States

One of the most significant impacts of climate change is the potential alteration of local hydrologic cycles over agriculturally productive areas. As the world’s food supply continues to be taxed by its burgeoning population, a greater percentage of arable land will need to be utilized and land currently producing food must become more efficient. This study seeks to quantify the effects of climate change on soil moisture in the American Midwest. A series of 24-year numerical experiments were conducted to assess the ability of Regional Climate Model Version 3 coupled to Integrated Biosphere Simulator (RegCM3-IBIS) and Biosphere-Atmosphere Transfer Scheme 1e (RegCM3-BATS1e) to simulate the observed hydroclimatology of the midwestern United States. Model results were evaluated using NASA Surface Radiation Budget, NASA Earth Radiation Budget Experiment, Illinois State Water Survey, Climate Research Unit Time Series 2.1, Global Soil Moisture Data Bank, and regional-scale estimations of evapotranspiration. The response of RegCM3-IBIS and RegCM3-BATS1e to a surrogate climate change scenario, a warming of 3oC at the boundaries and doubling of CO2, was explored. Precipitation increased significantly during the spring and summer in both RegCM3-IBIS and RegCM3-BATS1e, leading to additional runoff. In contrast, enhancement of evapotranspiration and shortwave radiation were modest. Soil moisture remained relatively unchanged in RegCM3-IBIS, while RegCM3-BATS1e exhibited some fall and winter wetting.