Data and Operational Processing for NASA's GPM Ground Validation Program

The Global Precipitation Measurement (GPM) satellite was launched by NASA and JAXA on February 27, 2014. For validation support, an extensive network of approximately 65 weather radars in different meteorological regimes were selected by the GPM GV (ground validation) program to identify biases between ground observations and satellite retrievals. Remote sensing by ground radars is a key element in bridging the space and time gap between satellite observations and in-situ surface instrumentation such as rain gauges and disdrometers. A majority of the radars (NOAA WSR-88D) were selected from the eastern United States to coincide geographically with products from the NOAA/NSSL ground-based National Mosaic and Multi-sensor Quantitative Precipitation Estimation (NMQ/MRMS). Additional radars are located on Pacific islands (Kwajalein Atoll - KPOL; Guam - PGUA; Hawaii - PHMO; PHKI), two Alaskan sites (PAIH; PAEC), one Pacific Northwest site (KLGX) and Puerto Rico (TJUA). There are two S-band dual-polarized research radars in the network, the CHILL radar (CSU - Greely, CO) and the mobile NASA polarimetric (NPOL) radar. NPOL data are available from the semi-permanent location near Wallops Flight Facility (Wallops Island, VA) and GPM field campaign locations (MC3E - Ponca City, OK; IFloodS - Traer, IA; and IPHEx - Rutherfordton, NC). GPM GV acquires WSR-88D Level II data in real time through the NEXRAD local data manger (LDM) stream. Raw SIGMET data from KPOL are provided daily by Atmospheric Technology Services Company (ATSC). NPOL data are retrieved locally, while CHILL data are received on a case-by-case basis. To begin the operational processing, GPM satellite coincidence files from the NASA Precipitation Processing System (PPS) are used to identify overpass details from each radar. When an overpass time is within 5 minutes of the radar data time stamp and nadir distance is within 200 km, the data are segregated for processing. Approximately thirty-five GPM overpass matches occur daily. Quality control is applied to the selected radar data using the NASA developed Dual Polarimetric Quality Control (DPQC) algorithm. In addition, NPOL and KPOL reflectivity and differential reflectivity are calibrated. Once the data are quality controlled and calibrated, numerous methods are used to provide rain rate estimates, hydrometeor classification, and drop size distribution retrievals. In this presentation; data acquisition, operational processing, product generation, and data distribution will be discussed.