Land-surface emissivity maps based on MSG/SEVIRI information

Retrieval of land-surface temperature (LST) using data from MSG/SEVIRI requires adequate estimates of land-surface emissivity (LSE). In this context LSE maps for SEVIRI channels IR3.9, IR8.7, IR10.8, and IR12.0 were developed based on the vegetation cover method. A broadband LSE map (3-14 μm) was also developed for estimating long-wave surface fluxes that may prove to be useful in both energy balance and climate modelling studies. LSE is estimated from conventional static classifications on land cover, LSE spectral data for each type of land cover, and fractional vegetation cover (FVC) information. Both IGBP-DIS and MODIS MOD12Q1 land cover products were used to build the LSE maps. Data on LSE were obtained from the JHU and JPL spectral libraries included in the ASTER spectral library, as well as from the MODIS-UCSB spectral library. FVC data for each pixel were derived based on NDVI. Depending on land cover type the LSE errors for channels IR3.9 and IR8.7 spatially vary from ± 0.6% to ± 24% and ± 0.1% to ± 33%, respectively, whereas the broadband spectrum errors lie between ± 0.3% and ± 7%. In the case of channels IR10.8 and IR12.0, 73% of the land-surfaces within the MSG disk present relative errors less than ± 1.5% and almost all (26%) of the remaining areas have relative errors of ± 2.0%. Developed LSE maps provide a first estimate of the ranges of LSE in SEVIRI channels for each surface type and obtained results may be used to assess the sensitivity of algorithms where an a priori knowledge of LSE is required.