Fate and Changes in Moisture Evaporated From the Tibetan Plateau (2000-2020)

Total evaporation from the vast terrain of the Tibetan Plateau (TP) may strongly influence downwind regions. However, the ultimate fate of this moisture remains unclear. This study tracked and quantified TP-originating moisture using an extended Eulerian model. The findings reveal that the involvement of moisture from the TP in the downwind precipitation is most pronounced near the eastern boundary of the TP and gradually diminishes eastward. Consequently, the TP moisture ratio in precipitation reaches the highest of over 30% over the central-eastern TP. 44.9%-46.7% of TP annual evaporation is recycled over the TP, and 65.1%-66.8% of the TP evaporation is reprecipitated over terrestrial China. Moisture recycling of TP origin shows strong seasonal variation, with seasonal patterns largely determined by precipitation, evaporation and wind fields. High levels of evaporation and precipitation over the TP in summer maximize local recycling intensity and recycling ratios. Annual precipitation of TP origin increased mainly around the northeastern TP during 2000-2020. This region consumed more than half of the increased TP evaporation. Further analyses showed that changes in reprecipitation of TP origin were consistent with precipitation trends in nearby downwind areas: when intensified TP evaporation meets intensified precipitation, more TP moisture is precipitated out. The model estimated an annual precipitation recycling ratio (PRR) of 26.9%-30.8% in forward moisture tracking. However, due to the non-closure issue of the atmospheric moisture balance equation, the annual PRR in backward tracking can be similar to 6% lower.