Decadal Variation in Raindrop Size Distributions in Busan, Korea

Cheol-Hwan You,Dong-In Lee

doi:10.1155/2015/329327

Abstract

This paper investigated the variability of raindrop size distributions (DSDs) in Busan, Korea, using data from two different disdrometers: a precipitation occurrence sensor system (POSS) and a particle size velocity (Parsivel) optical disdrometer. DSDs were simulated using a gamma model to assess the intercomparability of these two techniques. Annual rainfall amount was higher in 2012 than in 2002, as were the annually averagedDm(which was 0.1 mm greater in 2012) and the frequency of convective rain. Severe rainfall (greater than 20 mm h−1) occurred more frequently and with a largerDmin 2012. The values ofDmfrom July, August, and December, 2012, were much greater than from other months when compared with 2002. Larger raindrops contributed to the higher rain rates that were observed in the morning during 2012, whereas relatively smaller raindrops dominated in the afternoon. These results suggest that the increase in raindrop size that has been observed in Busan may continue in the future; however, more research will be required if we are to fully understand this phenomenon. Rainfall variables are highly dependent on drop size and so should be recalculated using the newest DSDs to allow more accurate polarimetric radar rainfall estimation.

Highlights

Drop size distributions (DSDs) provide important information for the microphysical structure of precipitation and describe the statistical distribution of falling raindrops’ size and number concentration
The average rainfall rates calculated from the simulated DSDs based on the precipitation occurrence sensor system (POSS) and Parsivel channel sizes were 20.3 and 20.1 mm h−1, respectively
To investigate the variation in DSDs obtained by POSS and Parsivel disdrometers during the years 2002 and 2012 in Busan, Korea, annual, monthly, and hourly distributions of three parameters (Dm, Nw, and shape) were calculated using a normalized gamma model

Summary

Introduction

Drop size distributions (DSDs) provide important information for the microphysical structure of precipitation and describe the statistical distribution of falling raindrops’ size and number concentration. Krajewski et al [17] showed that the Parsivel measures greater numbers of small drops (0.2 to 0.4 mm) than the 2DVD and generally reports higher rainfall rates. Thurai et al [15] found that the Parsivel records higher mass-weighted mean diameters and rainfall rates than the 2DVD, and this was most prominent when the rain rate was greater than 30 mm h−1. They noted that this is dependent on climatology.

Data and Methodology

Results

Summary and Concluding Remarks