Warming Tropical Indian Ocean Wets the Tibetan Plateau

Accurate detection and attribution of past climate change are crucial for projecting future climate change and formulating proper policies. In this study, we show that the warming of the tropical Indian Ocean contributes to the observed wetting trend in the Tibetan plateau. The warming tropical Indian Ocean can lead to more precipitation around the Arabian Sea. The associated diabatic heating triggers the cyclonic atmospheric response in the lower troposphere over the Arabian Sea and eastern Africa. It also causes the enhancement and westward extension of the western North Pacific subtropical high. The in-between airflow transports more moisture northward to the plateau, leading to the increased precipitation over the plateau. These large-scale circulation patterns can be detected from the long-term trends based on the observations and the large-ensemble historical simulations. They can also be simulated by an atmospheric general circulation model forced by the observed warming merely in the tropical Indian Ocean. The Tibetan plateau, often referred to the "Asian water tower," is the source region of many major rivers in Asia. It has experienced an increasing precipitation trend over the past few decades. In this study, we show that the warming tropical Indian Ocean contributes to this wetting trend. The warming tropical Indian Ocean can cause more precipitation around the Arabian Sea. The associated diabatic heating not only triggers an anomalous cyclone in the lower troposphere around the Arabian Sea and eastern Africa, but also causes the enhancement and westward extension of western North Pacific subtropical high. Consequently, the northward airflow between them transports more moisture to the plateau and causes more precipitation there. Our findings underscore the significant role of the warming tropical Indian Ocean in shaping the changing climate under global warming. Further research efforts are warranted to deepen our understanding of this phenomenon. The warming tropical Indian Ocean increases the precipitation over the Arabian Sea The associated large-scale circulation anomalies transport more moisture northward to the plateau Consequently, more moisture converges over the plateau, leading to the increased precipitation