Snowfall Measurements by Proposed European GPM Mission

The European Space Agency (ESA) is currently engaged in the study of the European Global Precipitation Measurement (EGPM) Mission. This represents both a dedicated ESA mission primarily supporting research and applications in the European Community and Canada, and a contributed spacecraft element and scientific research component for the International GPM Constellation Mission. The scientific payload of the EGPM satellite consists of a multispectral, conically scanning microwave radiometer and a 3-beam, nadir-pointing Ka-band rain radar. The radiometer operates at four window frequencies from cm to mm wavelengths (18.7, 36.5, 89.0, and 150.0 GHz), at one water vapor absorption frequency on the far wing of the 22.235 GHz H2O line (23.8 GHz), at four temperature sounding frequencies within 50-54 GHz on the low frequency wing of the 60 GHz molecular Oxygen complex, and at four complimentary-paired sounding frequencies in the vicinity of the strong 118.75 O2 line. The EGPM measurements will make contributions to a number of important scientific topics vis-à-vis precipitation science and the Earth's climatically varying water cycle. In this investigation, we examine the specific contribution of the EGPM satellite to snowfall measurement. This is achieved by synthetically calculating both the radiative observations generated by the EGPM radar - radiometer instrument suite and the consequent precipitation estimates for a numerically simulated snowstorm. The storm simulation is performed by means of a time-dependent, 3-dimensional, cloud/mesoscale model using explicit multi-species microphysics. The results demonstrate that because of its unprecedented sensor/channel capacity, the EGPM mission is expected to make significant improvements in the measurement of snowfall, to extend the observed precipitation spectrum as retrieved from space, and ultimately to improve the understanding and closure of the global water cycle.