Impacts of Synoptic and Regional Factors on Heat Wave Events over Southeastern Region of Korea in 2015

Abstract

In this study, the impacts of synoptic and regional factors on heat waves occurred over southeastern region of Korea in 2015 are investigated using a cluster analysis and numerical experiments. Heat wave events during 1980-2016 defined by three spatiotemporal criteria are classified into three clusters by using the k-means clustering analysis method. Each cluster has different synoptic conditions related to the western North Pacific subtropical high and monsoon circulation around South Korea. In addition to the synoptic conditions, high temperature events over southeastern region of South Korea in 2015 summer can be further enhanced by regional factors such as soil moisture amount and a high mountain range. To examine the effect of the local conditions on the 2015 summer heat wave case in South Korea, numerical experiments using a high-resolution Weather Research and Forecasting (WRF) model are conducted. There are four experiments, which are CTL experiment with no change in topography and soil moisture, TOPO experiment with decreased topography height, and WET and DRY experiments with wet and dry anomalies of initial soil moisture. CTL experiment simulates higher minimum temperature at the lee side compared to TOPO experiment because of the Föhn effect. In particular, the effect is prominent when westerly wind passing through mountain blows and the difference of relative humidity between the mountain flanks is significant (i.e., nighttime of dry period). Due to the less (more) evaporation, DRY (WET) experiment with less (more) soil moisture simulates higher (lower) maximum temperature than CTL experiment during the daytime when solar radiation is relatively intense.