CIMSS Seminar Series:
21 February 2007
Handling IR emissivity spectrum in hyperspectral sounding retrieval
Jinlong Li
Retrieval of temperature, moisture profiles and surface skin temperature from infrared (IR) radiances requires the spectral information of surface emissivity. Using constant or inaccurate surface emissivity typically results in the large retrieval errors, particularly over the semi-arid or arid area where the variation of emissivity spectrum is large spectrally and spatially. In this research, a physically based algorithm has been developed to retrieve hyperspectral IR emissivity spectrum simultaneously with the temperature and moisture profiles. To make the solution stable and efficient, the hyperspectral emissivity spectrum is represented by the eigenvectors, derived from the laboratory measured hyperspectral emissivity database, in the retrieval process. Simulations are carried out with profiles over different land surface properties, results show that simultaneous retrieval of emissivity spectrum can improve the surface skin temperature as well as temperature and moisture profiles retrievals, particularly for the boundary layer moisture. The algorithm has also been applied to the Atmospheric Infrared Sounder (AIRS) radiance measurements of granule 11 for 8 September 2004, which covers a diversity of land surface types. The retrievals have then been compared with the ECMWF analyses and radiosonde observations, and shown a similar improvement revealed in the simulations.
