AN EAST ASIAN SUBTROPICAL SUMMER MONSOON INDEX DEFINED BY MOIST POTENTIAL VORTICITY

Based on synthetically calculated thermodynamic and kinetic features of the summer monsoon of East Asia, this article utilizes the moist potential vorticity (MPV) to define a new index of subtropical summer monsoon for this region, and uses the NCEP/NCAR data to analyze the variation features of the subtropical summer monsoon for the past 60 years. The result shows that this new index can well reflect the seasonal, interannual, interdecadal variations and abrupt climate change of the subtropical summer monsoon. Besides, correlation analysis of this new index and the data of 160 stations in China show that, in the high index year, the summer monsoon is strong, it rains more in North China and southwestern inland and South China’s coastal areas while it rains less in the areas near Changjiang River and Huaihe River; the opposite is true in the low index year. Lastly, through comparisons with the other four representative indexes, this new index has obvious advantages in denoting the summer rainfall in the areas near Changjiang River and Huaihe River.