Based on SOM (self-organizing maps) and EOF (empirical orthogonal function) methods, the dailymean and seasonal-mean summer precipitation patterns in Eastern China are analyzed and compared. Results show that the SOM method, compared with EOF, describes precipitation distributions more realistically. The spatial structures of summer precipitation patterns can be well explained by 850 hPa wind anomaly and 700 hPa specific humidity anomaly. As a posterior problem, 850 hPa height anomaly can well explain the corresponding precipitation area. However, as a prediction problem, due to other conditions such as moisture and temperature anomaly, the negative height anomaly in the numerical weather forecasting does not always indicate strong precipitation.

The climatically character of wind vectors at 100 hPa and 850 hPa level and the relationship between the tropical easterly current at the 100 hPa level and trop ical cyclone numbers in low and high frequency years were analyzed by using the data of NCEP/NCAR reanalysis and the tropical cyclone data from JTWC(Joint Typho on Warning Center) over the Arabian Sea,Bay of Bengal and the South China Sea during the period 19581998.The result shows that a high positive correlation be tween tropical easterly current and the number of tropical cyclone is found in the Arabian Sea,Bay of Bengal.However,such a positive correlation is not found in South China Sea.Because South China Sea is at the southeast of South Asia high,the domination of meridional wind makes the relationship between tropical cycl one numbers and the merridional wind at the 100 hPa level is higher than it between tropical cyclone numbers and tropical easterly.