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Advantages of using the generalized gamma (GG) model to represent raindrop size distribution (DSD) are discussed, especially when near-complete DSD spectra are considered. Measurements from three climatically different locations in the United States are used. The central approach is the use of double-moment normalization of the measured DSDs using two reference moments, together with an underlying or intrinsic shape, h(x), based on two shape parameters. Stability of h(x) is examined and illustrative examples are presented. It is shown that the modal GG-fitted h(x) representing semiarid and subtropical regimes (combined) provides equally good fits to those from outer rain bands (after landfall) of a Hurricane, a tropical storm, and a tropical depression event. We also show similarities with some recent studies which had used GG model and address the goodness-of-fit aspects of the model, especially when compared with the (much) more widely used standard gamma model. Finally, some applications of the modal GG-fitted h(x) in remote sensing and numerical modeling of microphysical processes are briefly considered.

The Global Precipitation Measurement (GPM) Mission Validation Network (VN) is a NASA software system run at Marshall Space Flight Center which geometrically matches three-dimensional precipitation retrievals from the GPM Core Observatory (CO) sensors to 118 international ground-based radars. To advance the capabilities for validation of the multi-satellite IMERG product, the GPM VN is being updated to integrate this Level-3 (gridded) product alongside GPM’s Level-2 (footprint) products (DPR, CORRA, GPROF). The updated GPM VN will enable the potential for tracing the origins of systematic and random errors back through IMERG into the source GPROF product at instances of GPM-CO overpasses. Furthermore, the GPM VN can support validation efforts to trace the origins of IMERG inaccuracies under a consistent framework across locations including North America (Eastern CONUS, Alaska, Hawaii), Brazil, and Pacific islands (e.g. Kwajalein). This first study with the updated GPM VN will assess the oceanic performance of IMERG V06B across different island sites, as well as stratify errors using the vertical profile of reflectivity and hydrometeor classification corresponding to the IMERG grid pixel. These results will help to inform improvements for future IMERG versions, as well as to aid the community in understanding the conditions under which IMERG can be aptly applied for research and societal applications.