AN EAST ASIAN SUBTROPICAL SUMMER MONSOON INDEX DEFINED BY MOISTURE TRANSPORT
LIANG Ping 1, TANG Xu 2, HE Jin-hai3, CHEN Long-xun 4 (1. Shanghai Climate Center, Shanghai 200030 China;2. Shanghai Meteorological Bureau, Shanghai 200030 China;3. Nanjing University of Information Science & Technology, Nanjing 210044 China;4. Chinese Academy of Meteorological Sciences, Beijing 100081 China)
Using daily NCEP/NCAR reanalysis dataset and observation rainfall data in China for the 1971-2000 period, a subtropical summer monsoon index has been defined by meridional moisture transport of the total atmosphere column. Results show that the subtropical summer monsoon index defined by the difference of meridional moisture transport between South China and North China can be used to describe the intensity of the subtropical summer monsoon. High (low) index is corresponding to strong (weak) subtropical summer monsoon. And the new index is well related to the summer rainfall over the middle and lower reaches of Yangtze River. In addition, the convergence of moisture transport from the west Pacific via the South China Sea and that from the North China may be responsible for the anomalously excessive summer rainfall over the middle and lower reaches of Yangtze River.