Implementation and validation of a new weather filter for reducing weather effect in the ASMR2 sea ice concentration data

Abstract. Passive microwave radiometers observe the Earth's surface under practically all weather conditions, providing continuous global sea ice distributions on a daily basis. Ice concentration (IC) is one of the most important sea ice parameters derived from brightness temperatures measured by the microwave radiometers. However, even at microwave frequencies, the brightness temperature data over open ocean areas are affected by adverse weather conditions, including atmospheric water vapor, cloud liquid water, and abnormal water waves. The net result is the retrieval of moderate sea ice concentration values in the open ocean where sea ice is not expected. The current sea ice algorithms make use of what is called a “weather filter” to correct false sea ice retrievals, but significant areas in the ice-free water that have the false ice cover still remain. In this study, an improved weather filter, namely the Advanced Weather Filter (AWF), that minimizes this problem, developed by Cho et al. (2023), was implemented to produce JAXA/AMSR2 sea ice concentration products of the Arctic for verification. The AWF was validated and shown to be very effective in selected study regions in the Arctic during the summer from 30 June to 3 July 2014 and the winter from 15 December to 18 December 2014, thereby supporting the integration of the AWF into the standard AMSR2 sea ice concentration product. The AWF should be broadly applicable and can be implemented in other satellite passive microwave ice concentration datasets.