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

Abstract

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.