A PHYSICS-BASED ALGORITHM FOR RETRIEVING LAND-SURFACE EMISSIVITY AND TEMPERATURE FROM EOS MODIS DATA/

We have developed a physics-based land-surface temperature (LST) algor ithm for simultaneously retrieving surface band-averaged emissivities and temperatures from day/night pairs of MODIS (Moderate Resolution Im aging Spectroradiometer) data in seven thermal infrared bands. The set of 14 nonlinear equations in the algorithm is solved with the statist ical regression method and the least-squares fit method, This new LST algorithm was tested with simulated MODIS data for 80 sets of band-ave raged emissivities calculated from published spectral data of terrestr ial materials in wide ranges of atmospheric and surface temperature co nditions. Comprehensive sensitivity and error analysis has been made t o evaluate the performance of the new LST algorithm and its dependence on variations in surface emissivity and temperature, upon atmospheric conditions, as well as the noise-equivalent temperature difference (N E Delta T) and calibration accuracy specifications of the MODIS instru ment. In cases with a systematic calibration error of 0.5%, the standa rd deviations of errors in retrieved surface daytime and nighttime tem peratures fall between 0.4-0.5 K over a wide range of surface temperat ures for mid-latitude summer conditions. The standard deviations of er rors in retrieved emissivities in bands 31 and 32 (in the 10-12.5 mu m IR spectral window region) are 0.009, and the maximum error in retrie ved LST values falls between 2-3 K.