Classifying meridional movement of the south Asian high: spatiotemporal characteristics, regional climate impacts and formation mechanisms

The South Asian High (SAH) is an important component of the Asian monsoon system. Studies have indicated that meridional movement of the SAH can exert substantial influences on the weather and climate over surrounding and remote regions. This study shows that the meridional movement of the SAH can be divided into three types. The first type represents the meridional movement of the whole SAH (WBSM). The second and third types represent the meridional movement of the western and eastern parts of the SAH, respectively (denoted as WSM and ESM). Variation in WBSM significantly affects temperature over the Iranian plateau, China, and the Indian subcontinent, as well as precipitation over the central and northern Indian subcontinent and the Yangtze River basin. Variation in WSM has a notable impact on temperature over eastern China, western and central Asia, and precipitation over the Indian subcontinent and the Huang-Huaihe River basin. In contrast, ESM predominantly modulates temperature over Eastern Europe and China. The formation mechanisms of these three types of SAH movement are examined further. The results showed that variation in WBSM is significantly influenced by the Arctic Oscillation. The WSM is closely related to the Circumglobal Teleconnection Pattern (CGT). Sea surface temperature anomalies in the tropical central and eastern Pacific also influence the WSM by inducing a CGT-like atmospheric wave train, which can be confirmed by AGCM simulations. In addition, the ESM is modulated by a mid-latitude atmospheric wave train, which is the second leading mode of atmospheric variability over mid-latitude.