Diagnosing Physical Mechanisms Leading to Pure Heat Waves Versus Pure Tropical Nights Over the Korean Peninsula

This study analyzes differences in the mechanisms leading to anomalously high-temperature weather events, such as heat waves and tropical nights, in Korea. We identify pure heat wave and pure tropical night events during the period from 1979 to 2016. Based on composite analyses for each case, we identify different mechanisms leading to pure heat waves and pure tropical nights. The structures including low-level atmospheric circulations, specific humidity, wind, and the atmospheric stability are quite different between pure heat waves and pure tropical nights. Pure heat waves occur under barotropic-like atmospheric conditions, with a stable low layer and dry air due to anomalous easterly winds over the Korean Peninsula. In contrast, pure tropical nights occur under baroclinic-like atmospheric conditions, with warm, humid air advected by southwesterly winds. These results indicate that above-normal levels of incoming shortwave radiation combined with adiabatic warming contribute to pure heat waves, whereas pure tropical nights are associated with above-normal longwave radiation and/or warm advection over the Korean Peninsula. This implies that different physical factors must be considered for accurate, regional-scale predictions of heat waves and tropical night events.