New Features of the Global Precipitation Measurement (GPM) Validation Network

Various enhancements have been added to the Global Precipitation Measurement (GPM) Validation Network (VN) to evaluate the GPM satellite’s instrument and data product performance. The GPM VN acquires data from the Dual-frequency Precipitation Radar (DPR) on GPM, the Precipitation Radar (PR) on the Tropical Rainfall Measuring Mission (TRMM) satellite, from microwave imagers on GPM, TRMM, and GPM constellation satellites, and from ground radar (GR) networks in the continental U.S. and participating international sites. The VN characterizes the variability and bias of precipitation retrievals between the satellite products and the GR in various precipitation regimes, with the goal of improving precipitation retrieval algorithms for the GPM instruments.

The core VN dataset consists of WSR-88D GR data and matching satellite orbit subset data, primarily covering the eastern US. TRMM data range from August, 2006 to the present, and GPM and constellation data range from March, 2014 to the present. New features of the VN include the extension of the observation network from 21 weather service ground radars in the southeast US to 66 radars covering most of the eastern half of the US, and a radar in Alaska was also added to the network. Additional comparison parameters have also been added to the VN. These include ground radar polarimetric variables (Zdr, Kdp, RHOhv), microphysical variables (Dzero, Nw), and hydrometeor type classifications. New visualization tools and statistical methods are now also available to help compare ground radar and GPM DPR measurements for validation purposes. The VN also now includes an experimental GPM Microwave Imager (GMI)-to-ground radar geometry matching technique. For this product, the GMI near-surface rain rate field from the GPM GPROF algorithm is matched to the GR reflectivity and dual-polarization fields a) along the GMI line- of-sight, and b) as a vertical column above the GMI surface.

The full VN software suite to produce the geometric match-up, and analyze and display these data is available to the scientific community as open source code. Additional information may be obtained from the GPM GVS home page at http://gpm.gsfc.nasa.gov/groundvalidation.html.