Retrieval of temperature profiles over sea ice with multisensor analysis: combination of the DMSP's SSM/I, OLS, and SSM/T1 sensors

Knowledge of the atmospheric temperature profile is of critical importance for climatological and meteorological studies. For the polar regions, especially in the southern hemisphere, in-situ measurements from radiosonde are extremely sparse. Only satellite measurements can provide this information with good spatial coverage. The Special Sensor Microwave Temperature sounder (SSM/T1) on the polar orbiting satellite in the Defense Meteorological Satellite Program (DMSP) is well suited to derive temperature profiles continuously. Operationally-used retrieval methods account for the influence of the surface by utilizing only the surface channel, and significant retrieval errors can appear in the lower troposphere. In polar regions the surface conditions are complex with mixtures of open water and different types of ice, which possess different emissivities and coverage in the footprints of SSM/T1. The authors have combined SSM/T1 data with coincident data from the Special Sensor Microwave Imager (SSM/I) and the Operational Linescan System (OLS) to get surface information, specifically ice concentration and surface temperature, from which the emissivities of open water and two ice types at a frequency of 50.5 GHz are estimated. The temperature retrieval algorithm is based on the constrained linear inversion method. Temperature profiles are retrieved for the Weddell Sea region during July 1992, and compared to radiosonde data from the German research vessel Polarstern. The results show that multisensor retrieval on the average gives a 1 K (rms) improvement in the lower troposphere (h<5 km).