Moisture Sources and Pathways of Annual Maximum Precipitation in the Lancang-Mekong River Basin

Abstract

Recent extremely heavy precipitation has led to substantial economic losses and affected millions of residences in the Lancang-Mekong River Basin (LMRB). This study analyzed the spatial-temporal characteristics of the annual maximum precipitation (R1X) of the LMRB and identified the moisture sources and pathways conducive to R1Xs using a Lagrangian back trajectory model. Results show that India Ocean and Bay of Bengal (IO/BOB), local evapotranspiration, and West Pacific Ocean and East China (WP/EC) are the three main moisture transport pathways of the R1Xs in LMRB, contributing 68.3%, 20.4% and 11.3% of the trajectories, respectively. R1Xs in the downstream eastern area are affected by tropical cyclones bringing large amounts of moisture from the WP/EC. As tropical cyclones shifted northward under climate change impact, more extreme precipitation occurred over the LMRB due to moisture coming from WP/EC, but those from the IO/BOB had decreased because of the slowdown of flows across the Equator.