Distinct impacts of two types of South Asian high on the connection of the summer rainfall over India and north China

Abstract

AbstractThis study reveals a distinct impact of two types of the South Asian highs (SAH)—the northern mode of the SAH (NSAH) and the traditional SAH in its entirety (ESAH)—on the relation between Indian and north China summer rainfall variation. Specifically, variation of the summer rainfall over India has a strong (weak) relation with that over north China in the anomalous NSAH (ESAH) years. In particular, in association with a reinforced and northwestward shifting NSAH, the westerly jet stream at upper‐level troposphere over mid‐latitude also enhances and shifts northward. This is accompanied by a significant circumglobal teleconnection (CGT)‐like atmospheric wave train over mid‐latitude, with two marked anticyclonic anomalies around western Asia and northeastern China. The associated southerly wind anomalies over tropical northern Indian Ocean transport more water vapour northward to India and lead to above‐normal rainfall there. In addition, the pronounced southerly wind anomalies over East Asia transport abundant water vapour to north China and also result in more rainfall over north China. The above‐normal summer rainfall and associated atmospheric heating over India help maintain the CGT wave train over mid‐latitude, which is beneficial to increasing rainfall over north China, and leading to a close connection between the Indian and north China summer rainfall variation. However, for the ESAH years, the summer rainfall anomalies over India are weak, which cannot induce an obvious CGT‐like wave train over mid‐latitude and thus have a weak impact on the rainfall over north China. Thereby, the relation between Indian and north China summer is weak for the ESAH years.