资源环境科技发展态势分析平台

Evidence has suggested a wetting trend over part of the Tibetan Plateau ( TP) in recent decades, although there are large uncertainties in this trend due to sparse observations. Examining the change in the moisture source for precipitation over a region in the TP with the most obvious increasing precipitation trend may help understand the precipitation change. This study applied the modified Water Accounting Model with two atmospheric reanalyses, ground- observed precipitation, and evaporation froma land surfacemodel to investigate the change inmoisture source of the precipitation over the targeted region. The study estimated that on average more than 69% andmore than 21% of the moisture supply to precipitation over the targeted region came from land and ocean, respectively. The moisture transports from the west of the TP by the westerlies and from the southwest by the Indian summermonsoon likely contributed themost to precipitation over the targeted region. The moisture from inside the region may have contributed about 18% of the total precipitation. Most of the increasedmoisture supply to the precipitation during 1979- 2013 was attributed to the enhanced influx fromthe southwest and the local moisture supply. The precipitation recycling ratio over the targeted region increased significantly, suggesting an intensified hydrological cycle. Further analysis at monthly scale and with wet- dryyear composites indicates that the increased moisture contribution was mainly from the southwest and the targeted region duringMay and September. The enhanced water vapor transport from the IndianOcean during July and September and the intensified local hydrological recycling seem to be the primary reasons behind the recent precipitation increase over the targeted region.