The Sensitivity of Latent Heat Flux to Changes in the Radiative Forcing: A Framework for Comparing Models and Observations

A climate model must include an accurate surface physics scheme in order to examine the interactions between the land and atmosphere. Given an increase in the surface radiative forcing, the sensitivity of latent heat flux to available energy plays an important role in determining the energy budget and has a significant impact on the response of surface temperature. The Penman-Monteith equation is used to construct a theoretical framework for evaluating the climatology of evapotranspiration and the sensitivity of latent heat flux to available energy. Regional Climate Model version 3 coupled to Integrated Biosphere Simulator (RegCM3-IBIS); RegCM3 with its native land surface model, Biosphere-Atmosphere Transfer Scheme 1e (RegCM3-BATS1e); and Flux Network (FLUXNET) micrometeorological tower observations are compared and contrasted using the developed methodology. RegCM3-IBIS and RegCM3-BATS1e simulate the observed sensitivity of latent heat flux to available energy reasonably well during the summer on average; however, there are significant variations in the monthly values. Additional information provided by the physically based Penman-Monteith framework is employed for identifying deficiencies and guiding improvements in models, allowing calibration of both the climatology of evapotranspiration and the sensitivity of latent heat flux to available energy.