Moisture Sources and Transport for Extreme Precipitation Over Henan in July 2021

Determining the sources of moisture for the devastating precipitation event over Henan in July 2021 helps understand the mechanisms of such extreme precipitation events. In this study, the moisture sources and transport trajectories for the event are investigated using a Lagrangian approach. Moisture is transported to Henan along three routes that are driven by the western Pacific subtropical high (WPSH), WPSH and the tropical cyclone In-Fa, as well as WPSH and the tropical cyclone Cempaka, respectively. The WPSH-In-Fa-driven air parcels have the highest moistening and precipitating efficiency among the three routes. Overall, southern China contributes the most to moisture sources (38.1%), followed by the western North Pacific (30.0%). The results indicate that the terrestrial and oceanic moisture over southern China-western North Pacific are both crucial for the extreme precipitation event over Henan. Plain Language Summary A rare record-breaking heavy rainfall event hit Henan, China, in July 2021. The flooding induced by rainfall caused tremendous disasters to the local population. Where such a large amount of moisture originated from is the main concern of this study. We found that moisture was transported to Henan through three routes. All three routes are related to the high-pressure system over the western Pacific. Two of the routes are also related to typhoon In-Fa and typhoon Cempaka. The moisture from the In-Fa-related route has the highest efficiency in converting to rainfall. Furthermore, southern China is the most important source of moisture, indicating the prominent role of the terrestrial water cycle in this extreme rainfall.

Automated summary

In this study, the sources and transport trajectories of moisture for the devastating precipitation event in Henan in July 2021 were investigated. The results showed that southern China and the western North Pacific are crucial sources of moisture for this extreme rainfall event.