Estimating rain microphysical characteristics using s-band dual-polarization radar in South Korea

Abstract

Raindrop size distribution (DSD) observed using a disdrometer can be represented by a constrainedgamma (C-G) DSD model based on the empirical relationship between shape (µ) and slope (Ʌ). The C-G DSD model can be used to retrieve DSDs and rain microphysical parameters from dual-polarization radar measurements of reflectivity (ZH) and differential reflectivity (ZDR). This study presents a new µ-Ʌ relationship to characterize rain microphysics in South Korea using a two-dimensional video disdrometer (2DVD) and Yong-in S-band dual-polarization radar. To minimize sampling errors from the 2DVD and radar measurements, measured size distributions are truncated by particle size and velocity-based filtering and compared with rain gauge measurement. The calibration biases of radar ZH and ZDR were calculated using the self-consistency constraint and vertical pointing measurements. The derived m-L relationship was verified using the mass-weighted mean diameter (Dm) and standard deviation of the size distribution (σm), calculated from the 2DVD, for comparison with existing µ-Ʌ relationships for Florida and Oklahoma. The Dm-σmrelationship derived from the 2DVD corresponded well with the µ-Ʌ relationship. The µ-Ʌ relationship derived for the Korean Peninsula was similar to Florida, and both generally had larger µ values than Oklahoma for the same Ʌ. The derived µ-Ʌ relationship was applied to retrieve DSD parameters from polarimetric radar data, and the retrieved DSDs and derived physical parameters were evaluated and compared with the 2DVD measurements. The polarization radar-based C-G DSD model characterized rain microphysics more accurately than the exponential DSD model. The C-G DSD model based on the newly derived µ-Ʌ relationship performed the best at retrieving rain microphysical parameters.