Simulated Climatology and Sensitivity of Latent Heat Flux over the Midwestern United States
Jonathan Winter, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge
A four-year numerical experiment was completed to assess the ability of RegCM3 coupled to Integrated Biosphere Simulator (RegCM3-IBIS) and RegCM3 with its native land surface model, Biosphere-Atmosphere Transfer Scheme 1e (RegCM3-BATS1e), to simulate the energy and water budgets over the Midwestern United States. The models were evaluated using NASA Surface Radiation Budget, FLUXNET micrometeorological tower observations, and Climate Research Unit Time Series 2.0. Analysis was completed at three sites: Bondville, IL; Park Falls, WI; and Little Washita Watershed, which is located near Chickasha, OK.
To examine the effects of a changing atmosphere, a surface physics model must also capture the sensitivity of water and energy fluxes to an increase in the radiative forcing. The Penman-Monteith equation is used to construct a physically-based framework for evaluating the climatology of evapotranspiration and the sensitivity of latent heat flux to available energy. RegCM3-IBIS, RegCM3-BATS1e, and FLUXNET observations are compared and contrasted using the developed methodology. Additional information provided by the physically-based Penman-Monteith framework is employed for detecting errors and guiding the calibration of models, allowing tuning of both the model climatology and sensitivity.