Quantifying precipitation moisture contributed by different atmospheric circulations across the Tibetan Plateau

Abstract

Precipitation over the Tibetan Plateau (TP) is generally influenced by the Asian monsoons, the westerlies, and the local circulation patterns. However, the exact contributions of these systems to different regions over the TP remain largely unknown. To reveal these, this study traced the origin of precipitation at four marginal and one central grid cells of the TP from 2011 to 2020. The results indicate that the Indian monsoon, the westerlies, and the local circulations are systems that exert influence on precipitation at a TP scale. The East Asian summer monsoon (EASM) is a sub-TP influencing system that mainly affects the eastern TP. Specifically, the influence of the Indian monsoon decreases rapidly from south to north while contributing 62.4–63.0 %, 30.5–32.9 %, and 7.8–8.0 % of precipitation in Grids South, Central, and North, respectively. The westerlies play a dominant role in Grids North (68.4–71.7 %) and West (52.8–54.0 %). They contribute the least 20.7–21.9 % in Grid East. The local circulations by themselves influence the strongest in Grids Central and East. The EASM’s influence is strengthened in summer with the representative source contributing ∼ 18.8 % in comparison to an annual contribution of 12.8–13.1 % in Grid East. The outbreak of the Indian monsoon brings abundant moisture to the TP and elevates its influence primarily in Grids South and West. With the arrival of the rainy season, the wet TP becomes a more powerful moisture source. Consequently, most grids see an apparent strengthening in the role by the TP from spring to summer.