The Improvement of HUT Model and Its Application in Snow Depth Inversion

HUT model (Helsinki university of technology snow emission model) is a semi-empirical radiative transfer model of passive microwave remote sensing of snow, and it considered the impact of soil, forests and atmosphere on brightness temperature receiving by the sensor. HUT model was able to simulate brightness temperature receiving by the sensor. This paper validated HUT model based on MWRI data mounted on FY-3B satellite. The results showed that there was a big difference between brightness temperature of HUT model simulation and brightness temperature of MWRI for 18.7 GHz horizontal polarization and 36.5 GHz horizontal polarization. So this paper improved the extinction coefficient formula. The model that used the improved extinction coefficient formula calculating extinction coefficient was called improved HUT model (IMPHUT model). The validation result of IMPHUT model indicated that:the bias of IMPHUT model for 18.7 GHz horizontal polarization and 36.5 GHz horizontal polarization were -0.91 K and -4.19 K respectively. However the bias of HUT model for 18.7 GHz horizontal polarization and 36.5 GHz horizontal polarization were 14.03 K and -16.33 K respectively. Simulation accuracy of IMPHUT model was greatly improved. Finally, genetic algorithm was used to inverse snow depth on January 20, 2013. The result showed that bias of inversion snow depth based on IMPHUT model was -6.79 cm. The inversion snow depth based on IMPHUT model which was superior to HUT model and Chang algorithm was in good agreement with the measured snow depth.