Abstract

A Lagrangian model -the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT)-is used to quantify changes in moisture sources and paths for precipitation over North China's Henan Province associated with tropical cyclone (TC) over the western North Pacific (WNP) during July-August of 1979-2021. During TC-active periods, an anomalous cyclone over the WNP enhances southeasterly and reduces southwesterly moisture transport to Henan. Accord-ingly, compared to TC-inactive periods, moisture contributions from the Pacific Ocean (PO), eastern China (EC), and the local area (Local) are significantly enhanced by 48.32% (16.73% versus 11.28%), 20.42% (9.44% versus 7.84%), and 2.89% (4.91% versus 4.77%), respectively, while moisture contributions from the Indian Ocean (IO), Southwestern China (SWC), Eurasia (EA), and the South China Sea (SCS) are significantly reduced by-31.90% (8.61% versus 12.64%),-16.27% (4.60% versus 5.50%),-8.81% (19.10% versus 20.95%), and-6.92% (12.18% versus 13.09%). Furthermore, the moisture transport for a catastrophic extreme rainfall event during 17-22 July ("21.7" event) influenced by Typhoon Infa is investigated. Compared to the mean state during TC-active periods, the moisture contribution from the PO was substantially increased by 126.32% (37.87% versus 16.73%), while that from IO significantly decreased by-98.26% (0.15% versus 8.61%) during the "21.7" event. Analyses with a bootstrap resampling method show that moisture contributions from the PO fall outside the +647 range, for both the TC-active and TC-inactive probability distributions. Thus, the "21.7" event is rare and extreme in terms of the moisture contribution from the PO, with the occurrence probability being less than 1 in 1 million times.