Abstract




Land surface emissivity is important in calculating upward longwave radiation from the surface. As a result of historical lack of observations land surface emissivity is currently set as constant in land surface models (for example, 0.96 in CLM and 1 in NCEP) while, in the real world, it varies with land type and season, with a value as low as 0.7 for some desert regions. Our previous research illustrates that constant emissivity in model induces an approximate error of 5-20Wm-2 into the surface energy budget for arid areas. The primary goal of this project is to
Earth Observing System (EOS) MODerate Resolution Imaging Spectroradiometer (MODIS) observes the surface emissivity at 1km resolution using 6 spectral bands. Before it can be used in CLM, MODIS spectral band emissivity must to be converted to broadband and to be scaled up to model grid cell resolution. In addition, we will compare MODIS emissivity with ASTER observations for validation. A series of sensitivity simulations are designed to examine the impacts of emissivity on the modeled sensib le heat flux (SH), latent heat flux (LE), and skin temperature (Tskin). Off-line NCAR CLM2.0 and coupled CAM2 with CLM2.0 (CAM2/CLM) will be used in this work.This proposal complements our ongoing NASA EOSIDS project to ensure we have adequate resources for this emissivity research. The global emissivity data set developed and examined here will directly improve NCAR community climate model and will be avai lable for other modeling centers