Variability of Summer Atmospheric Moisture Flux and Its Effect on Precipitation over East China

Using the in-situ precipitation and NCEP/NCAR daily reanalysis data, we found by studies of change ofmoisture flux and its effect that the northward water vapor transport represented by moisture flux in EastChina tends to retreat southward, and the eastward water vapor transport tends to weaken with weakeningof the intensity of moisture flux. The north boundary of meridional moisture flux (50 kg m-1s-1) retreats2.8 degrees in latitude per decade during 1968-2003. The weakening of water vapor transport implies theweakening and southward retreat of East Asian monsoon, which leads to the tendency of decrease in moistureflux convergence over North China and the middle and lower reaches of the Yellow River, and the tendencyof decrease in precipitation over those regions, but on the contrary the enhanced water vapor transportconvergence over the middle and lower reaches of the Yangtze River implies the tendency of increase inprecipitation to some extent. Indeed the long-term variability of precipitation in East China has a closerelation with that of atmospheric moisture flux.