GPM Radar Studies at NASA's Wallops Precipitation Research Facility

The Wallops Precipitation Research Facility has been established to support NASAs Global Precipitation Measurement (GPM) Ground Validation (GV) program. The facility consists of a large suite of instruments (e.g. rain gauges, profilers, and disdrometers), as well as a number of radars providing dual-polarization observations at several different frequencies including W-, Ka/Ku-, and S-bands. The W-band (93.93 GHz) Aerosol, Cloud, Humidity, Interactions Exploration and Validating Enterprise (ACHIEVE) is a fully deployable mobile laboratory containing active and passive sensors for measuring cloud, aerosols, and precipitation properties. ACHIEVEs primary instrument is a scanning dual-polarization pulsed-Doppler radar. Its high resolution capability (typically 25 to 50 m), 0.25 degree beam width, and high sensitivity of the radar (-55 dBZ at 1 km) allows for detection of small-scale changes in cloud structure owing to changes in particle size distribution characteristics, and is usually operated in a vertically oriented (profiling) mode. NASAs Dual-frequency, Dual-polarized, Doppler radar (D3R) provides matched-beam (0.9 degrees) measurements at both Ka- and Ku-bands, near those on board the GPM core satellite, using a state-of-the-art solid-state transmitter and receiver operating with a peak power 200 W (Ku)/40 W (Ka). D3R is capable of scanning in PPI sector, RHI, surveillance, and vertically pointing mode to a maximum range of approximately 40 km. NASAs dual-POLarization (NPOL) radar is a dual polarimetric S-band radar, with a 0.95 beam width and a peak power of 840 kW, providing high quality observations beyond 100 km. NPOL is also capable of scanning in both horizontal and vertical modes. During the spring of 2015, both the ACHIEVE and D3R radars were collocated at Wallops Flight Facility, while the NPOL radar was deployed in Newark, MD about 40 km to the north. We will present comparisons of observations from these radars during two long duration precipitation events (20 April 2015 and 26 April 2015) to demonstrate how they can be used in synergy to provide critical observations for developing particle size distribution characteristics and variability in both the horizontal and vertical, including ice characteristics, melting layer physics and DSD/PSD parameters and correlations. We will show that by using targeted scans with these multi-parameter radars over a dense network of gauges and disdrometers, a focused effort toward characterizing errors as functions of scale, physics, platform, and approach is possible.