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Abstract

Liquid water has a significant impact on the microwave emissivity of the surface and, since decade, passive microwave observations are using to detect melt over ice sheet. However, the produced indicators are usually based on a single frequency and have different sensibilities. In the framework of the ESA 4D-Antarctica project, we propose to combine the binary melt indicators from the single-frequency to provide enhanced insights of the melt process. We focus on the 36 GHz and 19 GHz observations from the Advanced Microwave Scanning Radiometer 2 (AMSR2) satellite and the 1.4 GHz observations from the Soil Moisture and Ocean Salinity (SMOS) satellite. A deep theoretical analysis has been performed to explore the sensitivity of these frequencies to wet snow. In particular, 36 GHz distinguishes different stage of close surface melting and 1.4 GHz identifies the most intense period of melt during the summer. Moreover, AMSR2 provides observations in the afternoon (ascending pass) and in the night (descending pass) to detect the possible presence of a refrozen surface layer. The final classification is composed of nine melt status, which allows determining if a melt event was limited to the surface or if it was intense enough to inject significant water amounts at depths, and if refreezing happens during the night. This new product provides a clear and synthetic description of the melt status along the season. This opens a good opportunity for a potential use for the Copernicus Imaging Microwave Radiometer (CIMR) perspective.