Abstract: The differences between mean monthly zonal wind anomalies at 850 hPa and 200hPa are defined as the South China Sea Tropical Monsoon Index (STMI), the Walker Circulation Index (WKCI) and the Tropical Circulation Intensity Index (TCIX), and the significance of these indexes for synoptic climatology is discussed. TCIX, which is the difference between STMI and WKCI, has a close relation with the summer precipitation in China, especially in the Yangtze River basin. Based on the correlation analysis between TCIX and 500 hPa height fields, SLP, SST and OLR for winter, spring and summer, the possible influence of TCIX on the summer precipitation in China is revealed. The interseasonal variation of TCIX and the correlation with the ambient field of earlier stage are usefull for the forecast of summer rain belts.