Retrieval and sensitivity analysis of the atmospheric inversion layer based on Fengyun satellite infrared hyperspectral data

Atmospheric inversion layer will hinder the development of vertical movement. Traditionally, only ground-based radiosonde data are used for monitoring and analyzing the atmospheric inversion layer. Spaceborne hyperspectral infrared atmospheric sounding can retrieve atmospheric temperature and humidity profiles in clear sky condition, which provides a possible technique for monitoring the atmospheric inversion layer. In order to explore the method of monitoring inversion layer using domestic satellite data, the RTTOV fast radiative transfer model is used to simulate the FY-3D/HIRAS observation spectrum, including the effects of different inversion strength and height of the inversion layer top on the brightness temperature observed by HIRAS. The results show that the channels corresponding to the fine spectral lines in the window region of 780—1000 cm⁻¹ are most sensitive to the inversion layer, and the brightness temperature difference between the observed channel and the reference channel (926.875 cm⁻¹) can be used to identify the atmospheric inversion layer. The sensitivity index of inversion strength and the sensitivity index of the height of the inversion layer top are defined in this study. Simulation results show that the sensitivity indices of inversion strength at strong absorption (784.375 cm⁻¹, 798.750 cm⁻¹), medium absorption (803.125 cm⁻¹, 852.500 cm⁻¹) and weak absorption (840.000 cm⁻¹, 871.250 cm⁻¹) channels are 0.49, 0.48 and 0.30, and the sensitivity indices of the height of the inversion layer top are 0.045, 0.036 and 0.018, respectively. Based on the brightness temperature of the strong absorption channels, the inversion strength and the height of the inversion layer top can be retrieved, and the correlation of the channel brightness temperature with inversion strength is higher than that with the height of the inversion layer top. The results verify the applicability of using infrared hyperspectral channel brightness temperature data to study the inversion layer structure, and provide a basis and reference for subsequent retrievals of the inversion characteristics.