Variation of Precipitation and Water Vapor Transport over the Northwest China from 1959 to 2005

NCEP/NCAR reanalysis data and a 47-year precipitation dataset from145 observation stations had been utilized to analyze the characteristics of variation of precipitation and water vapor transport in Northwest China.The results showed that:(1)Northwest China had different regional climatic characteristics in different areas.The interannual trends of precipitation between the eastern Northwest China(ENWC)and the western Northwest China(WNWC)showed a contrary variation.In the middle 1980s,the precipitation continually decreased in ENWC,but in WNWC the precipitation appeared an upward trend.(2)In summer,the water vapor of the ENWC was mainly from the Bay of the Bengal,the South Sea and the West Pacific Ocean.The northerly Siberia and the middle-latitude westerly water vapor transport had influenced on the WNWC in summer.(3)The western and southern boundaries were the main inflow passports for the ENWC,and the western boundary was the main inflow passport for the WNWC.In more precipitation years,the water vapor flux arrived at a peak point in July and had a obvious interannual change.(4)The water vapor influx into western and southern boundaries appeared downward trend in ENWC,but in WNWC the water vapor influx into the western boundaries was upward in the middle 1980s.