A Study of the Effects of using Subgrid Version of BATS (SUB-BATS), Coupled with RegCM, on Simulation of Surface Temperature and Rainfall over Iran

Because of the heterogeneous nature of land surface the interaction of scales poses a significant problem in coupling models of the atmosphere and biosphere، climate models now have spatial resolution of order of a few hundred kilometers. One of the best approaches among different methods to gain benefits of entering subgrid processes is using a high resolution surface model say subgrid version of BATS (Biosphere-Atmosphere Transfer Scheme) coupled with the atmospheric model. Numerical experiments using the 3rd Version of the Regional Climate Model (RegCM3)، coupled with the Biosphere-Atmosphere Transfer Scheme (BATS)، are performed to study the role of entering subgrid scale effects of moisture، energy and momentum fluxes from heterogeneous land surfaces on simulation of temperature and rainfall over Iran. Evaluation of model simulations against the Climate Research Unit (CRU) observational data shows that RegCM3 is generally successful in simulating the precipitation and temperature fields. However، the simulated precipitation is considerably higher than observations in the high-lands، in part due to the CRU''s lack of enough observations for the mountainous areas of the region.