Rain on snow (ROS) understudied in sea ice remote sensing: a multi-sensor analysis of ROS during MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate)

Abstract. Arctic rain on snow (ROS) deposits liquid water onto existing snowpacks. Upon refreezing, this can form icy crusts at the surface or within snowpack. By altering radar backscatter and microwave emissivity, ROS over sea ice influence accuracy of variables retrieved from satellite altimetry, scatterometers, passive radiometers. During Ocean MOSAiC (Multidisciplinary drifting Observatory for Study Climate) expedition, there was an unprecedented opportunity to observe a event using in situ active instruments similar those deployed platforms. accumulation snowpack increased melt, 4-fold decrease energy returned Ku- Ka-bands. After refroze layers formed, followed by 6-fold increase energy. Besides backscatter, analysis waveforms shows waveform shape changed response refreezing. Microwave emissivity 19 89 GHz with increasing content decreased as refroze, yet subsequent altered polarization difference. Corresponding CryoSat-2 well AMSR2 brightness temperatures further that refreeze were significant enough impact returns. Our provides first detailed impacts refreezing both observations, providing important baseline knowledge detecting assessing their satellite-derived variables.