Interdecadal Variation in the Relationship Between Ground Heat Flux over the Tibetan Plateau and Heatwave in Korea

This study investigates the relationship between ground heat flux (GHF) over the Tibetan Plateau and heatwave days in Korea. A weak negative correlation was found during the pre-1998 period (1979 to 1997), whereas a strong positive correlation emerged during the post period (1998 to 2019). To further examine the mechanisms underlying this interdecadal change, seven positive and seven negative GHF years were selected for both the pre-1998 and post-1998 periods and composite analyses were conducted. During positive GHF years in the post-1998 period, the Tibetan Plateau experienced enhanced surface heating, reduced spring snow cover, and lower summer soil moisture. These conditions favored greater absorption and release of heat from the land surface. Concurrently, anomalous anticyclonic circulation strengthened throughout the troposphere, accompanied by enhanced subsidence over the latitude band containing the Korean Peninsula. In addition, both the western North Pacific high and the South Asian high expanded and intensified during positive GHF years, exerting a stronger influence on the middle and upper troposphere over Korea. The increased occurrence of heatwaves in Korea during the post-1998 period is partly attributable to enhanced thermal forcing over the Tibetan Plateau and the associated development of a circumglobal teleconnection-like wave train, which induced downstream anticyclonic circulation anomalies over East Asia. This upper-tropospheric forcing, together with a La Niña–like or negative Pacific Decadal Oscillation–like sea surface temperature pattern, created atmospheric conditions favorable for more frequent heatwave events over Korea. These results suggest that the influence of Tibetan Plateau thermal forcing on Korean heatwaves has strengthened since the late 1990s through its interaction with large-scale atmospheric circulation and oceanic background conditions.