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Title: Variability of raindrop size distribution and its impact on polarimetric rain rate estimators
Authors: Jyothi, K Amar
Rao, T N
Keywords: Raindrop size distribution (DSD);Rainfall estimation;Polarimetric variables;Scattering coefficient
Issue Date: Aug-2012
Publisher: NISCAIR-CSIR, India
PACS No.:; 92.60.jf
Abstract: Four years of raindrop size distribution (DSD) by Joss-Waldvogel (JW) Disdrometer measurements made at Gadanki (13.5°N, 79.2°E) have been used to derive relations for rainfall estimation from polarimetric radar variables. The polarimetric variables are estimated in X-band (at 9.368 GHz, the chosen frequency for the radar being developed at Gadanki) from the observed DSD measurements and scattering amplitudes derived using T-matrix scattering simulations. Three rainfall estimators, namely R-Z, R-KDP and R-(ZH, ZDR), are derived for both stratiform and convective types of rain. Also, following the earlier reports, which highlighted the large variability of DSD between the seasons, the above relations are derived for three seasons (pre-monsoon, southwest monsoon and northeast monsoon). The scatter plots of R and Z show large scatter around the regression fits, even after separating the data into different seasons and types of rain, indicating the large and complex variability of DSD. Among all the relations, R-Z relation depends heavily on the DSD with its coefficients vary significantly between the seasons and types of rain. The other two relations show weak dependency on DSD, however, the coefficients are found to be distinctly different from those reported elsewhere. Both qualitative and quantitative evaluation analyses on a case study reveal that R-(ZH, ZDR) relation provides better R among the three relations.
Page(s): 471-480
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.41(4) [August 2012]

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