Retrieval of Three-Dimensional Raindrop Size Distribution Using X-Band Polarimetric Radar Data

Abstract

An improved algorithm based on the self-consistent principle for rain attenuation correction of reflectivity Z H and differential reflectivity Z DR are presented for X-band radar. The proposed algorithm calculates the optimum coefficients for the relation between the specific attenuation coefficient and the specific differential phase, every 1 km along a slant range. The attenuation-corrected Z DR is calculated from reflectivity at horizontal polarization and from reflectivity at vertical polarization after attenuation correction. The improved rain attenuation correction algorithm is applied to the range-height indicator (RHI) scans as well as the plan position indicator (PPI) volume scan data observed by X-band wavelength (MP-X) radar, as operated by the National Research Institute for Earth Science and Disaster Prevention (NIED) in Japan. The corrected Z H and Z DR values are in good agreement with those calculated from the drop size distribution (DSD) measured by disdrometers.The two governing parameters of a normalized gamma DSD, normalized number concentration N W , and drop median diameter D 0 are estimated from the corrected Z H and Z DR , and specific differential phase K DP values based on the ''constrained-gamma'' method. The method is applied to PPI and RHI data of a typhoon rainband to retrieve the three-dimensional distribution of DSD. The retrieved DSD parameters show reasonable agreement with disdrometer data. The present results demonstrate that high-quality correction and retrieval DSDs can be derived from X-band polarimetric radar data.

Quantitative Precipitation Estimation and Hydrological Modeling in Japan

“…The signal attenuation error is a common problem associated with the use of weather radar for QPE (Ryzhkov and Zrnic, 1995;Carey et al, 2000;Anagnostou et al, 2004;Matrosov et al, 2005;Park et al 2005;Maki et al 2005;Germann et al, 2006;Kim et al, 2010). Different algorithms have been developed to eliminate the attenuation error for different radar bands in in various environments (Carey et al, 2000;Matrosov et al, 2005;Park et al, 2005;Kim et al, 2010).…”

“…Different algorithms have been developed to eliminate the attenuation error for different radar bands in in various environments (Carey et al, 2000;Matrosov et al, 2005;Park et al, 2005;Kim et al, 2010). A significant disadvantage of X-band wavelengths is the signal extinction area.…”

“…This signal extinction problem can be solved by using data from entire radar observation networks . Park et al (2005) and Kim et al (2010) corrected for the attenuation effect in the Kanto region of Japan using X-band polarimetric weather data (MP-X Ebina).…”

Algorithm for the Identification and Tracking of Convective Cells Based on Constant and Adaptive Threshold Methods Using a New Cell-Merging and -Splitting Scheme

“…Kim et al (2010) developed a sophisticated method of attenuation correction for dual-polarimetric radar; however, the problem of attenuation effects has yet to be resolved for conventional radar using shorter wavelength (e.g., X-band). AITCC does not implement an attenuation correction scheme; however, conventional attenuation correction for convective precipitation (Doviak and Zrnić 1993) should be applied prior to running AITCC.…”

Observational operators for dual polarimetric radars in variational data assimilation systems

“…These radars provide polarimetric parameters, including the horizontally polarized reflectivity factor (ZH), the vertically polarized reflectivity factor (ZV), differential reflectivity (ZDR), and the specific differential phase (KDP). Many QPE methods that use these parameters have been proposed (e.g., Jameson, 1991;Jameson and Caylor, 1994;5 Ryzhkov and Zrnić, 1995;Anagnostou et al, 2008;Kim et al, 2010;Ryzhkov et al, 2014;Adachi et al, 2015). Because QPE methods using dual polarimetric radar parameters is expected to be better than methods using single polarization radar data, we developed assimilation methods for dual polarimetric radar observations for both WRF Var and NHM-4DVAR.…”