Variations of PM10 concentration in South Korea in response to typhoon activity in the South China Sea

Abstract

This thesis has investigated the relationship between typhoon activity over the western North Pacific and particulate matter ≤ 10 μm diameter (PM10) concentration in South Korea. Among all 345 typhoons for the period 2001 –2016, 26% of tham indicated maximum PM10 concentration during life time when they occurred in the South China Sea (SCS

110°E –130°E and 10°N –25°N). For the composite analysis of 219 typhoons passing through the SCS, a tilted Rossby wave like pattern appeared from subtropics (SCS) to high latitudes (the Kamchaka peninsula). In South Korea, anomalous high pressure, shallow boundary layer, and warm air temperature are observed, which are favorable to increase PM10 concentration. The Rossby wave-like feature varied according to season and typhoon intensity. The wave amplitude was smaller, and the wave propagated more to South Korea in autumn than in summer. The wave amplitude had stronger when typhoon intensity was stronger, contributing higher PM10 concentration in South Korea. The PM10 transboundary transport from Chian is also important contribution to PM10 concentration increase in South Korea. Based on 72-hour back trajectories from the HYSPLIT model, the 219 typhoons in the SCS are divided into three types according to source region

local, continental and oceanic types. The local and oceanic types showed similar Rossby wave-like pattern, while in the continental type, a wide low pressure anomaly condition is dominant over South Korea which is hard to be seen as the Rossby wave pattern. The stable condition which can be referred as shallow boundary layer height and warm temperature appear in the local and oceanic type, however, it does not be seen in the continental type. Mean PM10 concentration of continental type is the highest, followed by local and oceanic type. Finally, among the combination of season, tropical cyclone (TC) intensity, and PM10 source types except the continental type, a group of strong TC in the SCS with local type in autumn shows the largest increase of PM10 concentration (17.2 μg m-3 higher than seasonal mean 37.7 μg m-3) of 21 typhoons. Therefore, this thesis suggests that the effect of typhoon activity over the SCS on PM10 concentration in South Korea should be considered when we study the variation of the PM10 concentration.