Three distinct convective footprints over the Indo-western Pacific that affect high temperature extreme events in Korea during boreal autumn

Abstract

This study identified three distinct convection structures over the Indo-western Pacific that caused high-temperature extreme (HTE) events in Korea during the boreal autumn season based on k-means clustering analysis. These three clusters commonly involve barotropic high-pressure anomalies over East Asia that act as essential components for driving HTE events. However, the dynamical atmospheric teleconnection pathways from the Indo-western Pacific to East Asia for the three clusters were distinguishable. The convection structure of the first cluster exhibited a meridional tripole pattern from the eastern Indian Ocean to East Asia and was strongly associated with phase 5 of the Madden Julian Oscillation (MJO). In response to these convective heating anomalies, high-pressure anomalies over East Asia are induced by the northeastward propagating low-level atmospheric wave train and are also affected by the zonally elongated high-pressure system within the upper atmosphere. In contrast, the HTE events in Korea for the second cluster are derived from enhanced convection over the northeastern Indian Ocean that acts as the atmospheric heat source that generates an eastward atmospheric wave train, thus forming a high-pressure anomaly over East Asia. Finally, the third cluster represents the response of El Niño and positive Indian Ocean dipole, showing a sharp contrast of convection between the western Indian Ocean and the eastern Indian Ocean/western Pacific. The impacts of the third cluster on the Korean HTE primarily stem from Rossby wave trains forced by convective heating anomalies around the tropical Indo-western Pacific. Through analysis of the dynamical variables, detailed descriptions of the physical characteristics of the three distinct clusters of Indo-western Pacific convection are presented in this study, and possible implications for autumn climate variability over East Asia and Korea are also provided.