Fate and changes in moisture evaporated from the Tibetan Plateau (2000-2020)

Abstract

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. The results show that the TP moisture participation in downwind regions' precipitation is the strongest around the eastern edge of the TP and then weakens gradually toward the east. Consequently, TP moisture in the composition of precipitation over the central-eastern TP is the largest of over 30%. 44.9-46.7% of TP annual evaporation is recycled over the TP, and about 2/3 of the TP evaporation is reprecipitated over terrestrial China. Moisture cycling 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 ˜6% lower.

The disproportionate impact of enhanced evaporation from melting arctic sea ice on cold-season land precipitation trends

“…The evaporated moisture from the AMS was computationally tracked in the framework of the Water Accounting Model-2layers (WAM-2layers) 44,51 . WAM and its derived public data 52 have been widely used in the study of moisture recycling 53,54 , atmospheric moisture tracking [55][56][57] and the influence of hydrological cycle changes 58,59 . The underlying principle for moisture tracking from a specific region (Ω) is the atmospheric water balance, which is reflected in the moisture transport within and between layers (l, either the bottom or the top layer) in WAM-2layers as follows:…”