A possible optimum rainfall estimation algorithm using

In this study, to get an optimum rainfall estimation using polarimetric variables observed from Bislsan radar which is the first polarimetric radar in Korea, rainfall cases for 84 hours caused by different conditions, which are Changma front and typhoon, Changma front only, and typhoon only, occurred in 2011 were analyzed. And rainfall algorithms were developed by using long period drop size distributions with six different raindrop axis ratio relations.

Normalized error, fractional root mean square error (RMSE), and correlation coefficient of rainfall relations were calculated using rainfall recorded at 121 gages within radar coverage for 84 hours. There was different rainfall relation with raindrop shape assumptions and rainfall intensity. The relation between rainrate (R) and specific differential phase (KDP), differential reflectivity (ZDR) was the worst performance and the relation between R and horizontal reflectivity (Z), ZDR had the best score in all raindrop shapes. The specific attenuation (AH) was calculated by observed differential phase shift (ÔDP) and Z and the rainfall relations using AH were also calculated and analyzed.

The relations between R and Z, ZDR, R and KDP, ZDR, and R and KDP were the best RMSE at the light rain, medium rain, and high rainfall regime, respectively. The relation between R and Z, ZDR, KDP, and AH and R and Z, KDP, AH were relatively good performance in all rainfall regime. The combination of the relations between R and Z, ZDR, and R and KDP, ZDR, and R and KDP with different rainfall intensity would be an optimum rainfall algorithm if the reference of rainfall would be defined correctly. In the case the reference is not defined adequately, the relation between R and Z, ZDR, KDP, AH and R and Z, KDP, AH can be used a representative rainfall relation. Especially if the qualified ZDR is not available, the relation between R and Z, KDP, AH can be used as an optimum rainfall relation in Korea.