Land Surface Emissivity retrieval from the measurements of FengYun-2 satellites

Abstract

This work addressed the Land Surface Emissivity (LSE) retrieval over west China region from combined Middle InfraRed (MIR) and Thermal InfraRed (TIR) data of the Stretched Visible and Infrared Spin Scan Radiometer (SVISSR) aboard the Chinese first generation geostationary satellites FengYun-2C (FY-2C) and FengYun-2D (FY-2D). To improve the retrieval accuracy, the SVISSR/FY-2 infrared channels 1 (∼10.9µm), 2 (∼11.9µm), 4 (∼3.8µm) were intercalibrated with the well-calibrated AIRS/Aqua and MODIS/Terra channels in tropical regions using the Ray-Matching (RM) method and High Spectral Convolution (HSC) method. The atmospheric effects were removed from SVISSR/FY-2 data using MODTRAN fed with ECMWF (European Center for Median-range Weather Forecast) data. Based on the concept of Temperature Independent Spectral Indices of Emissivity (TISIE) constructed with one channel in MIR and the other in TIR, and assuming that the TISIEs do not change between day and night, the land surface emitted and reflected radiances in SVISSR/FY-2 MIR channel in a clear-sky daytime can be first separated, and then the directional reflectances at different angles were obtained. Finally, LSEs were modeled with the RossThick-LiSparse-R BRDF (Bidirectional Reflectance Distribution Function) model and the Kirchhoff's law.