COMPARISON OF LAND-SURFACE CLIMATOLOGY OF THE NATIONAL CENTER FOR ATMOSPHERIC RESEARCH COMMUNITY CLIMATE MODEL 2 AT R15 AND T42 RESOLUTIONS

Land surface climatologies averaged over the last 5 years of 10-year seasonal cycle integrations of the National Center for Atmospheric Research community climate model 2 (CCM2) with the Biosphere-Atmosphere Transfer Scheme (BATS) land surface option configured for R15 and T42 resolutions were compared. Both simulations had a large warm-temperature bias over northern hemisphere land regions in July. The CCM2 without BATS has a similar bias, which BATS, with its interactive hydrology, accentuated. Both simulations had too much precipitation, which is also a feature of CCM2 without BATS. Most differences in continental-averaged hydrologic and surface energy fluxes between the R15 and T42 simulations were minor for January and July (<0.4 mm d-1 and < 11 W m-2). Only 5 of 14 continental-scale comparisons showed larger differences. In two of these, differences in land surface hydrology and energy exchange between the R15 and T42 simulations were related to precipitation differences, possibly from changes in the cloud fraction parameterization of CCM2 in its R15 and T42 configurations. The spatial resolution of the model was also important for the Mississippi Basin, where the T42 model was hotter and drier than the R15 model. These analyses show that improved spatial resolution does not necessarily result in continental-averaged land surface climatologies substantially different from those of lower-resolution models but that the improved resolution can be important at regional scales.