Land surface emissivity from high temporal resolution geostationary infrared imager radiances

The time continuity of measurements from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard the Meteosat Second Generation (MSG) Meteosat-8/9 and from the Advanced Baseline Imager (ABI) onboard the next generation of Geostationary Operational Environmental Satellite (GOES-R) can be uniquely taken into account for infrared (IR) land surface emissivity (LSE) retrievals. The algorithm is based on the assumption that land surface temperature (LST) is temporally variable while the LSE is temporally invariable within a short period of time, i.e. a few hours. SEVIRI/ABI radiances from multiple time steps can be used to retrieve temporally invariable IR LSE and variable LST. The algorithm theoretical basis is described. Sensitivity studies with simulations show that 1) the algorithm is less sensitive to the first guesses of LST and the 8.7 µm LSE, but quite sensitive to the first guesses of the 10.8 and 12 µm LSE; 2) the algorithm is less sensitive to the observational noise and radiative transfer calculation uncertainty (in the form of random noise); and 3) except for the 8.7 µm LSE, the algorithm is less sensitive to the radiance biases in the 8.7 µm channel from dust contamination, but sensitive to the radiance biases in the 12 µm channel from the radiative transfer calculation. It is also found that the algorithm is sensitive to the LST weighting functions rather than the sensor's local zenith angle (LZA); as long as the LST weighting functions are large enough, the retrieval precision is good.