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- Title
Sensitivity of C-Band Polarimetric Radar-Based Drop Size Estimates to Maximum Diameter.
- Authors
Carey, Lawrence D.; Petersen, Walter A.
- Abstract
Estimating raindrop size has been a long-standing objective of polarimetric radar-based precipitation retrieval methods. The relationship between the differential reflectivity Zdr and the median volume diameter D0 is typically derived empirically using raindrop size distribution observations from a disdrometer, a raindrop physical model, and a radar scattering model. Because disdrometers are known to undersample large raindrops, the maximum drop diameter Dmax is often an assumed parameter in the rain physical model. C-band Zdr is sensitive to resonance scattering at drop diameters larger than 5 mm, which falls in the region of uncertainty for Dmax. Prior studies have not accounted for resonance scattering at C band and Dmax uncertainty in assessing potential errors in drop size retrievals. As such, a series of experiments are conducted that evaluate the effect of Dmax parameterization on the retrieval error of D0 from a fourth-order polynomial function of C-band Zdr by varying the assumed Dmax through the range of assumptions found in the literature. Normalized bias errors for estimating D0 from C-band Zdr range from −8% to 15%, depending on the postulated error in Dmax. The absolute normalized bias error increases with C-band Zdr, can reach 10% for Zdr as low as 1-1.75 dB, and can increase from there to values as large as 15%-45% for larger Zdr, which is a larger potential bias error than is found at S and X band. Uncertainty in Dmax assumptions and the associated potential D0 retrieval errors should be noted and accounted for in future C-band polarimetric radar studies.
- Subjects
RAINDROP size; RAINDROPS; METEOROLOGICAL precipitation; RADAR polarimetry; METEOROLOGICAL research
- Publication
Journal of Applied Meteorology & Climatology, 2015, Vol 54, Issue 6, p1352
- ISSN
1558-8424
- Publication type
Article
- DOI
10.1175/JAMC-D-14-0079.1