韓半島 雨雹 特性에 관한 硏究

Abstract

This study analyzed the characteristics of hail events in Korean peninsula. Observed data for the research was set from the hail reports by 47 weather stations over South Korea. Data were selected for each case when the hail size was over 0.5cm for 29 years(1972~2000). 1992 was the most frequently observed year with 16 reports, while 1999 the rarest year with just 3. The analysis of the dates on the reports showed that the events have 10 year period frequency. The average number of hail days for 1970's was estimated to be 10.6, while 9.5 for 1980s', and 8.0 for 1990s'. Consequently, it is considered that the hail events had slight declining mode. Among twelve months, November showed the most frequent events with 86 times. Also, It showed some tendency that the events occurred more frequently during El Nino regime, and vise versa (during La Nina regime). The most probable hour for the events turned out to be 14:00~18:00, afternoon. On the other hand, during the summer season, many cases were reported that the hail was made even in the morning hours. The hail size gradually increased from February when it showed the smallest. In August it grew up to 1.1cm. Although as freezing level appears relatively high in summer, giving bad environment for the hail to comes up, abundant moisture in the air helps it to have big size. For 7 months from April to October, more cases accompanied lightings with hail events than those of the rest months. Synoptic fields during the days before hail events showed that upper jet stream appears away, south from the Korea. Meanwhile, low level jet showed up at 850 hPa over the region. Dew-point depression at 850 hPa, 700 hPa was 1.2℃ and 1.4℃ for each. It could be thought that the moist air and the strong wind made intensive moisture flux in the system. Particularly, 500 hPa pressure field showed that "right-tilted pouch" pattern had not made any hail event. According to the hail occurrence conceptual model of the Korean Peninsula, the ground convergence rate is above 10, but the upper level divergence was above 10. The Buoyancy was 1,757 J/㎏, EL with 9,624 m, FL with 3,191 m, CCL with 2,324 m, MVV with 47 m/s and Echo-Top reached to 11 km in the conceptual model which the active hail may be potentially occurred. Finally, from the sounding analyzed, only 12 hours before the hail event, upper atmosphere looks very dry while lower atmosphere evaporated. And the values told that the tendency diminished at the time of the hail events. Instability was well informed by TTs index. The values at the events showed over 50.