Based on the NCEP/NCAR reanalysis data,an investigation has been carried on the climatologically structural and evolutional features of the East Asian subtropical summer monsoon trough(STSMT) and its comparison with the South China Sea summer monsoon trough(SCSSMT).

The seasonal variations of the intensity and location of the East Asian subtropical Westerly Jet(EAWJ) and its thermal mechanism are analyzed by using the NCEP/NCAR monthly reanalysis data from 1961 to 2000.

Using the monthly mean reanalysis datasets from the NCAR/NCEP,relationships of the interannual variation between an eastern Asia[CD*2]Pacific dipole(APD) mode and the East Asian subtropical monsoon are studied.

The progress is reviewed briefly of research on the East Asian tropical and subtropical monsoons by Chinese meteorologists,which involves the features of Asian tropical monsoon onset with its mechanisms,and the index design,associated circulation systems,low frequency oscillations,interannual and interdecadal variations of the East Asian monsoon.

With 1958 - 1997 NCEP/NCAR reanalysis data and 1961 - 1995 summer (JJA) rainfall and temperature records of 160 stations in China, a new East Asian subtropical summer monsoon circulation index is defined, in which the barotropic and baroclinic components of the circulation are included.

The monthly wind field of NCEP/NCAR reanalysis data is used to define an intensity index of the East Asia subtropical westerly jet, which can reasonably reflect the impact of the East Asia subtropical westerly jet on summer precipitation in North China.