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Andy Heymsfield

Senior Scientist, Mesoscale and Microscale Meteorology Laboratory, NCAR

Development of Triple Wavelength Snowfall and Rainfall Rate Relationships to Radar Reflectivity from Collocated Aircraft In-Situ and Overflying Radar Data and from Global Satellite Radar Measurements

Room 811 AOSS, March 27, 2017, 3:30 PM


In this study, two methods for deriving relationships between the equivalent radar reflectivity factor (Ze) and the snowfall rate (S) at three radar wavelengths are described: from quasi-direct measurements, and by assuming there is conservation of mass flux (precipitation rate) across the melting layer (ML). In the first method, data from collocations of in-situ aircraft (microphysical observations) and overflying aircraft (2 and 3-wavelength radar observations) from two field programs are used to develop relationships. In the second method, Ze measurements from radars on the satellites Tropical Rain Measuring Mission (TRMM), Global Precipitation Measurement (GPM), and CloudSat, at the top of the ML and retrieved rainfall rate R at the base of the ML draw upon the concept that the mass flux through the ML is approximately constant. Retrievals of R are likely to be more reliable than S due to the far fewer assumptions involved in the retrieval and supporting ground-based validation data. The collocation data sets represent yield about 20,000 times when the two aircraft were within 2 km horizontally at a given time. Ze-S relationships are developed for the collocations and the mass flux technique, and compared to those derived from level 2 retrievals from the standard satellite products and a number of relationships developed earlier. It is shown that the there are substantial differences-and improvements made, through use of the relationships developed here.

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