The Dynamic Plateau Monsoon Index and Its Association with General Circulation Anomalies

Based on monthly ECMWF reanalysis-Interim (ERA-Interim) reanalysisdata, along with monthly precipitation and temperature data, the DynamicPlateau Monsoon Index (DPMI) is defined. The results of a contrast analysis ofthe DPMI versus the Traditional Plateau Monsoon Index (TPMI) are described. Theresponse of general circulation to northern Qinghai-Xizang Plateau summermonsoon anomalies and the correlation of the DPMI with general circulationanomalies are investigated. The results show that, the DPMI reflectedmeteorological elements better and depicted climate variation more accuratelythan the TPMI. In years when the plateau summer monsoon is strong, the low overthe plateau and the trough near the eastern coast of Asia are deeper and higherthan normal over South China. This correlation corresponds to two anomalouscyclones over the plateau and the eastern coast of Asia and an anomalousanticyclone in South China. The plateau and its adjacent regions are affectedby anomalous southwesterly winds that transport more moisture to South Chinaand cause more precipitation. The lower reaches of the Yangtze River appear toreceive more precipitation by means of the strong westerly water vapor flowtransported from the ``large triangle affecting the region". In years when theplateau summer monsoon is weak, these are opposite. The plateau monsoon isclosely related to the intensity and position of the South Asian high, and theexistence of a teleconnection pattern in the mid-upper levels suggests apossible linkage of the East Asian monsoon and the Indian monsoon to theplateau summer monsoon.