A GENERALIZED SPLIT-WINDOW ALGORITHM FOR RETRIEVING LAND-SURFACE TEMPERATURE FROM SPACE

We propose a generalized split-window method for retrieving land-surfa ce temperature (LST) from AVHRR and MODIS data, Accurate radiative tra nsfer simulations show that the coefficients in the split-window algor ithm for LST must vary with the viewing angle, if we are to achieve a LST accuracy of about 1 K for the whole scan swath range (+/-55 degree s from nadir) and for the ranges of surface temperature and atmospheri c conditions over land, which are much wider than those over oceans, W e obtain these coefficients from regression analysis of radiative tran sfer simulations, and we analyze sensitivity and error over wide range s of surface temperature and emissivity and atmospheric water vapor ab undance and temperature, Simulations show that when atmospheric water vapor increases and viewing angle is larger than 45 degrees, it is nec essary to optimize the split-window method by separating the ranges of the atmospheric water vapor, lower boundary temperature, and the surf ace temperature into tractable subranges. The atmospheric lower bounda ry temperature and (vertical) column water vapor values retrieved from HIRS/2 or MODIS atmospheric sounding channels can be used to determin e the range for the optimum coefficients of the split-window method, T his new algorithm not only retrieves land-surface temperature more acc urately, but is also less sensitive to uncertainty in emissivity and t o instrument quantization error.