Microphysical Analysis of Snowfall using S-band Polarimetric Radar in South Korea

The relationship between radar reflectivity factor and snowfall rate has been a long standing issue to be solved because of its great dependence on the density, the types, and fall velocity. Thanks to the advent of dual polarization radar, the observations of winter precipitation from polarimetric radar provides insights into the microphysical properties of the snowfall.

The goal of this study is to describe the microphysical characteristics of snowfalls in terms of the polarimetric variables such as radar reflectivity Z, differential reflectivity Z_DR, cross-correlation coefficient ρ_HV and specific differential phase K_DP. The S-band polarimetric radar (a test-bed of Weather Radar Center in Korea, called YIT) and the two-Dimension Video Disdrometer (2DVD) were used to classify the snowfall types and examine the their characteristics.

Snowfall events for data analysis were selected from the winter seasons (December, January, and February) from the years 2014 to 2016. To investigate the vertical structure of snowfall with time, quasi-vertical profiles (QVPs, Kumjian et al. 2013; Ryzhkov et al. 2015) were obtained from 13.2 elevation angle data of YIT radar. The high reflectivity cores, sometimes reaching to 30 dBZ with Z_DR values close to 0 dB or even below 0 dB. The high Z/low Z_DR cores near the surface were associated with aggregation, in other hand, the low Z/high Z_DR cores in the 2-3km height were associated with dendrite growth zone. The variations of ρ_HV and Z_DR were also related to these solid precipitation types. The particle fall velocity measured from the 2DVD would be one of possible parameters which can identify the snowfall types in these snowfall events. The performance of various snowfall relations were also examined for various events.

Acknowledgment

This work was funded by the Korea Meteorological Industry Promotion Agency under Grant KMIPA 2015-1050.