Modulation of Anomalous Moisture Uptakes on Weather-Type-Based Daily Extreme Precipitation Events over the Southeastern Edge of the Tibetan Plateau

Abstract The southeastern edge of the Tibetan Plateau (SETP) is prone to severe extreme precipitation events (EPEs), causing huge damages by triggering water-related hazards during summer season. Given the complexity of weather systems and the intricate nature of terrain, the formation mechanisms of the EPEs and related water cycle processes remain unclear. Here, based on 38-yr Lagrangian simulations and moisture source diagnosis, we show that the anomalous moisture uptakes for the daily EPEs exhibit an analogous “tripole pattern,” with Southeast Asia acting as the dominant contributor (fractional contribution, 74.5%), followed by the Arabian Sea (9.7%), the Bay of Bengal (9.5%), and the Tibetan Plateau (6.3%). Under different weather types (WTs), the moisture uptakes exhibit dramatic contrasts, which are largely shaped by the shift and intensity of the west Pacific subtropical high, the surface thermodynamic conditions over Southeast Asia, and the cyclonic anomaly over the tropical ocean. The thermodynamic characteristics of the underlying surface over those anomalous moisture supply “hotspots” identified here, together with the corresponding favorable atmospheric circulation pattern, thereby could potentially serve as the precursors for EPEs over the SETP. Significance Statement The southeastern edge of the Tibetan Plateau (SETP) is subject to frequent extreme precipitation events (EPEs) that cause huge damages by triggering water-related hazards during summer season. In spite of its significance, anomalous moisture uptakes for the EPEs over SETP are understudied. Here, an ensemble Lagrangian numerical modeling and moisture source diagnostics are adopted to quantify the anomalous moisture sources of the EPEs associated with weather types. The results provide insights into the formation mechanisms of EPEs by studying many cases in historical data. Furthermore, the valuable information on the anomalous moisture uptakes and associated synoptic circulation patterns serves as a supplemental precursor and thereby could potentially enhance the predictive skill of EPEs, which is undoubtedly beneficial to disaster prevention and mitigation.