韓半島 集中豪雨 特性分析 - 장마기와 장마 후의 사례를 중심으로

Abstract

An attempt is made to analyse characteristic features of heavy rainfall which occurs at the metropolitan area in the Korean peninsular during the on- and off- Changma season. For this, two representative heavy rainfall episodes are selected; as the one during the on-Changma season, a torrential rain episode happened at Goyang city on 12 July 2006 and as the other during the off-Changma season, a heavy rainfall event in Seoul on 21 September 2006. Both recorded considerable amount of precipitation over 250mm in a half-day, which exceeded much more the amount expected by numerical prediction models at those times and caused a great damage to the property and life in the affected area. It is analysed that in spite of the seasonal differences, two cases all were due to the strong instability locally developed on the quasi stationary front, rather than by the developed or systematic cyclone. Similarities in characteristics of both episodes were shown in the location of upper-level jet streak and divergence fields of the upper wind over heavy rainfall areas, significantly high equivalent potential temperatures in the low atmospheric layer due to the entrainment of hot and humid air by the low-level jet, and the existence of very dry air and cold air pool in the middle layer of the atmosphere at the peak time of the rainfall. Those factors brought convective instability in the atmosphere, which is analysed as one of the major reasons of the heavy rainfall at those times. Whereas, a few distinct differences exist between the events. Among them, differences in dynamic features of the low-level jet and the position of rainfall area along the low-level jet are remarkable.

Key words: heavy rainfall, on- and off-Changma, convective instability, upper and low-level jet, dry and cold air pool