A Consistent Treatment of Microwave Emissivity and Radar Backscatter for Retrieval of Precipitation over Water Surfaces

作者：Munchak S Joseph^*; Meneghini Robert; Grecu Mircea; Olson William S

来源：Journal of Atmospheric and Oceanic Technology, 2016, 33(2): 215-229.

DOI：10.1175/JTECH-D-15-0069.1

• Satellite observations
• Filtering techniques
• Mathematical and statistical techniques
• Observational techniques and algorithms
• Radars/Radar observations
• Microwave observations

The Global Precipitation Measurement (GPM) Microwave Imager (GMI) and dual-frequency precipitation radar (DPR) are designed to provide the most accurate instantaneous precipitation estimates currently available from space. The GPM Combined Radar-Radiometer Algorithm (CORRA) plays a key role in this process by retrieving precipitation profiles that are consistent with GMI and DPR measurements; therefore, it is desirable that the forward models in CORRA use the same geophysical input parameters. This study explores the feasibility of using internally consistent emissivity and surface backscatter cross-sectional (
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) models for water surfaces in CORRA. An empirical model for DPR Ku- and Ka-band
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as a function of 10-m wind speed and incidence angle is derived from GMI-only wind retrievals under clear-sky conditions. This allows for the
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measurements, which are also influenced by path-integrated attenuation (PIA) from precipitation, to be used as input to CORRA and for wind speed to be retrieved as output. Comparisons to buoy data give a wind rmse of 3.7 m s(-1) for Ku+GMI retrievals and 3.2 m s(-1) for Ku+Ka+GMI retrievals under precipitation (compared to 1.3 m s(-1) for clear-sky GMI-only retrievals), and there is a reduction in bias from the global analysis (GANAL) background data (-10%) to the Ku+GMI (-3%) and Ku+Ka+GMI (-5%) retrievals. Ku+GMI retrievals of precipitation increase slightly in light (<1 mm h(-1)) and decrease in moderate to heavy precipitation (>1 mm h(-1)). The Ku+Ka+GMI retrievals, being additionally constrained by the Ka reflectivity, increase only slightly in moderate and heavy precipitation at low wind speeds (<5 m s(-1)) relative to retrievals using the surface reference estimate of PIA as input.

• 出版日期2016-2