What Can We Learn from the CloudSat Radiometric Mode Observations of Snowfall over the Ice-Free Ocean?

The quantification of global snowfall by the current observing system remains challenging,with the CloudSat 94 GHz Cloud Profiling Radar (CPR) providing the current state-of-the-art snowclimatology, especially at high latitudes. This work explores the potential of the novel Level-2CloudSat 94 GHz Brightness Temperature Product (2B-TB94), developed in recent years by processingthe noise floor data contained in the 1B-CPR product; the focus of the study is on the characterizationof snow systems over the ice-free ocean, which has well constrained emissivity and backscatteringproperties. When used in combination with the path integrated attenuation (PIA), the radiometricmode can provide crucial information on the presence/amount of supercooled layers and on thecontribution of the ice to the total attenuation. Radiative transfer simulations show that the locationof the supercooled layers and the snow density are important factors affecting the warming causedby supercooled emission and the cooling induced by ice scattering. Over the ice-free ocean, theinclusion of the 2B-TB94 observations to the standard CPR observables (reflectivity profile andPIA) is recommended, should more sophisticated attenuation corrections be implemented in thesnow CloudSat product to mitigate its well-known underestimation at large snowfall rates. Similarapproaches will also be applicable to the upcoming EarthCARE mission. The findings of this paperare relevant for the design of future missions targeting precipitation in the polar regions.