Variation Characteristics of Water Vapor Transport and Precipitation in the Three Rivers' Headstream Region during the Recent Several Decades

Based on daily meteorological factors at observation stations and daily reanalysis data (including daily wind and daily specific humidity) of NCEP/NCAR I Reanalysis data during 1971-2010, temporal-spatial distributions and variation characteristics of water vapor transport and precipitation in the Three Rivers’ Headstream Region were analyzed. The results showed that the temporal-spatial distributions of water vapor transport and precipitation were similar in the Three Rivers’ Headstream Region, but that variation characteristics were different in recent several decades. During 1971-2010, meridional water vapor transport showed the dramatic decreasing trend due to the decrease of water vapor transport on southern boundary, and zonal water vapor transport showed the significantly increasing trend due to the decrease of water vapor transport on eastern boundary. Water vapor budget in the whole region had the same decreasing trend as the meridional water vapor transport, while precipitation had a certain increasing tendency without passing the significance testing. Water vapor transport decreased significantly in the Three Rivers’ Headstream Region especially in the southern-east part during 1971-2010, while water vapor transport in June and September decreased most. At the same time, the degree of convergence of water vapor flux divergence in lower-layer atmosphere reduced. However, annual precipitation didn’t show the significantly decreasing trend in recent decades, except that precipitation in September decreased obviously.