Precipitable water conversion rates over the Qinghai-Xizang (Tibet) Plateau: changing characteristics with global warming

In this article, the trends and variability of precipitation and precipitable water (PW) over the Qinghai-Xizang (Tibet) Plateau (QXP) (19702009) were analysed by using ERA-40 (The European Center for Medium-Range Weather Forecasts (ECMWF) 40 years Re-analysis) and NCEP (The National Centers for Environmental Prediction)/NCAR reanalyses data and the ground observed precipitation data from 60 sites. The results showed that the precipitation over the QXP had an overall increasing trend; however, a slight decreasing trend was observed over the southeast. This decreasing precipitation trend might be related to the South Asia monsoon degradation. Since 1970, a decreasing PW trend has occurred over the QXP in which the southeast is the most significant region. Because of the rising temperatures in the QXP, a remarkable PW conversion rate (PWCR) increase of 0.87% per decade has occurred over the past 40?years. Because of its steep terrain, the PWCR in the middle eastern region of the QXP increased faster than that of the other regions. The mean PWCR in the wet southern region of the QXP was higher than that of the dry northern region, which was higher in the winter than that in the summer. Although much precipitation occurred in the summer, in the wet regions, the PWCR was higher in the winter than in the summer. The PWCR peak in the wet and dry regions occurred during the precipitation-short and precipitation-sufficient seasons, respectively. Copyright (c) 2011 John Wiley & Sons, Ltd.