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

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.11Nsciescopu

The non-linear relationship between the western North Pacific anticyclonic circulation and Korean summer precipitation on subseasonal timescales

It has been widely known that the pulse of the western North Pacific anticyclonic circulation (WNPAC) plays a key role on East Asian summer climate variability in subseasonal to interannual time scales. Yet, the relation between the WNPAC and summer precipitation over Korea is not robust on seasonal and subseasonal timescales for the recent few decades. Here, we show that the low correlation between WNPAC and Korean precipitation is attributable to their distinctive non-linear relationship and investigate detailed features in their four different phase relationships on subseasonal time scales. First, the positive Korean precipitation anomaly occurs as the part of zonally elongated precipitation band along with the positive WNPAC anomaly closely connected with the decaying phase of El Nino and Indian Ocean warming. The second case is enhanced Korean precipitation accompanying with negative WNPAC anomaly. In this case, the negative WNPAC anomaly constitutes a part of atmospheric wave train across the North Pacific and this feature is associated with the decaying phase of La Nina. The typhoon-related precipitation event also contributes to this case. Third, the negative Korean precipitation anomaly arises when the low-level easterly anomaly along with the northern flank of negative WNPAC anomaly leads to suppressed convective activity in Korea. Lastly, the negative Korean precipitation anomaly happens with the positive WNPAC anomaly when anomalous high covers entire East Asia and the WNP mainly during the decaying phase of central Pacific El Nino. The understanding of the non-linear relationship between WNPAC and Korean precipitation in this study provides better insight into the potential impacts of El Nino-Southern Oscillation and circulation/convection anomaly over the WNP on summer Korean precipitation.11Nsciescopu