We introduced daily crop development and growth functions into theBiosphere-Atmosphere Transfer Scheme (BATS) coupled to the National Center for Atmospheric Research Regional Climate Model (NCAR RegCM2). Coupled RegCM/BATS simulations were performed over the conterminous United States for a dry (1988) and a favorably moist (1991) growing seasons at a spatial resolution of 90 x 90 km. We found that differences in air and ground temperature, mixing ratio, and precipitation between these two seasons were significantly larger in the interactive cases compared to the control ones. The differences in interannual variability were due to the fact that the interactive version of the model was able to capture extensive plant wilt that resulted from drought conditions of summer 1988, the control version was not. Inhibited plant growth resulted in significant decreases in the surface moisture flux to the atmosphere, therefore increasing the sensible heat flux. This acted as a positive feedback to the climate model's suggested dry conditions of 1988. The interactive version of RegCM/BATS that we developed agreed better with observations for the maximum daily air temperature over the central Great Plains for each of the two years in question compared to the control version. Interannual variability ranges simulated with the interactive version of the model also agreed better with observations compared to control ones.
The principal objective of this paper is to investigate the effect, over a predominantly agricultural central U.S. domain, of the interactively-simulated crop development and growth on the interannual variability in the warm-season surface and air temperature, mixing ratio, and precipitation. Heat, moisture, and momentum fluxes over land strongly depend on the condition of surface vegetation. Experimental data indicate that some biophysical parameters (Leaf Area Index, bulk canopy resistance, roughness length) vary significantly throughout the growing season.
