GPM Snowfall Retrievals: Information Gained from Day 1 GPROF Empirical Databases

An empirical a priori database using coincident CloudSat-derived surface precipitation rates and microwave radiometer observations was created to facilitate Day 1 Global Precipitation Measurement (GPM) Goddard Profiling Algorithm (GPROF) precipitation retrievals. This empirical database matches multi-frequency brightness temperature observations from the Advanced Microwave Scanning Radiometer-EOS (AMSR-E) and Microwave Humidity Sounder (MHS), thus containing a similar channel selection as the GPM Microwave Imager (GMI). The CloudSat/AMSR-E/MHS a priori database is currently used for precipitation retrievals over very cold surface types and provides critical information for Day 1 GPROF high latitude snowfall retrievals. This study presents results from an exhaustive analysis of higher latitude snowfall events contained in this dataset. Initially, the CloudSat snowfall dataset is independently evaluated against ERA-Interim snowfall accumulations for various surface types. The CloudSat surface snowfall rate dataset is then binned by two-meter temperature (T2m), total precipitable water amount (TPW), and surface emissivity type (SFC) in accordance with the GPROF retrieval scheme. This binning procedure allows us to determine snowfall event occurrence and snowfall rate intensity populating the respective GPROF T2m/TPW/SFC bins. The a priori database is also partitioned by snowfall type (e.g., shallow versus deep cloud structures) to show systematic trends within the GPROF bins classified by snowfall morphology. Lastly, the preliminary GPM database is binned by T2m and TPW to compare against the CloudSat database.