Comparison of Raindrop Size Distribution between NASA’s S-Band Polarimetric Radar and Two-Dimensional Video Disdrometers

• Published in: Journal of applied meteorology and climatology Vol. 59; no. 3; pp. 517 - 533
• Main Authors: Tokay, Ali, D’Adderio, Leo Pio, Marks, David A., Pippitt, Jason L., Wolff, David B., Petersen, Walter A.
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center American Meteorological Society 01.03.2020
• Subjects: Accuracy; Aeronautics; Algorithms; Calibration; Comparative analysis; Comparative studies; Datasets; Diameters; Disdrometers; Global precipitation; Meteorology And Climatology; Parameters; Polarimetric radar; Precipitation; Quality control; Radar; Radar polarimetry; Rain; Raindrop size distribution; Raindrops; Rainfall; Reflectance; Satellite observation; Satellites; Size distribution; Studies; United States > US
• ISSN: 1558-8424; 1558-8432; 1558-8432; 1558-8424
• DOI: 10.1175/JAMC-D-18-0339.1

The ground-based-radar-derived raindrop size distribution (DSD) parameters—mass-weighted drop diameter D mass and normalized intercept parameter NW —are the sole resource for direct validation of the National Aeronautics and Space Administration (NASA) Global Precipitation Measurement (GPM) mission Core Observatory satellite-based retrieved DSD. Both D mass and NW are obtained from radar-measured reflectivity ZH and differential reflectivity Z DR through empirical relationships. This study uses existing relationships that were determined for the GPM ground validation (GV) program and directly compares the NASA S-band polarimetric radar (NPOL) observables of ZH and Z DR and derived D mass and NW with those calculated by two-dimensional video disdrometer (2DVD). The joint NPOL and 2DVD datasets were acquired during three GPM GV field campaigns conducted in eastern Iowa, southern Appalachia, and western Washington State. The comparative study quantifies the level of agreement for ZH , Z DR, D mass, and log(NW ) at an optimum distance (15–40 km) from the radar as well as at distances greater than 60 km from radar and over mountainous terrain. Interestingly, roughly 10%–15% of the NPOL ZH –Z DR pairs were well outside the envelope of 2DVD-estimated ZH –Z DR pairs. The exclusion of these pairs improved the comparisons noticeably.