Retrieval of Geophysical Parameters from MODIS Measurements: Extension of a Two-Step Algorithm

An extension has been made to the current two-step physical retrieval algorithm. The "extended" version simultaneously retrieves an atmospheric temperature-humidity profile, skin temperature and surface emissivity under an assumption that surface emissivity remains constant between daytime and nighttime radiometric observations. This assumption will typically be met in the absence of recent precipitaion. Preliminary study based on MAS simulation data has demonstrated that combining daytime and nighttime observations and retaining the surface-reflected solar beam improve the retrieval of atmospheric and surface parameters. Particularly, surface skin temperature and shortwave IR surface emissivity RMSE are 40% and 70% smaller, respectively. More studies will be made with considering wide range of changes in atmospheric and surface conditions. The extended algorithm will be applied to real observations from the MAS and MODIS sensors.