Analysis of the water vapor transport process and characteristics of the rainstorm in Hefei in July 2021

Abstract

[Objective] In the context of global climate change, climate variability has increased sharply, and extreme events have become more frequent, posing significant threats to people's lives, property, and the healthy development of the socio-economic system. During the 2021 Meiyu season in Anhui Province, the average rainfall was 317 mm, which was nearly 30% higher than the long-term average. To analyze the moisture transport field of heavy rainfall and reveal its development characteristics, [Methods]the Lagrangian Hybrid Single Particle Trajectory Model(HYSPLIT) was utilized to simulate the moisture transport trajectories during the rainfall event in the Dongpu and Dafangying reservoir basins of Hefei City in July 2021. [Results] The result indicate that the spatial distribution of rainfall was uneven, with an average rainfall of 306.6 mm. The highest rainfall was recorded at Liumiao Station(356.5 mm), while the lowest was at Shenyoufang Station(228.5 mm). The characteristics of moisture transport trajectories varied at different height levels. At 925 hPa, there were southeast paths from the Western Pacific, southwest paths from the Bay of Bengal, and southward paths from the South China Sea, with corresponding moisture contribution rates of 44.4%, 43.8%, and 11.8%, respectively. At 850 hPa, the paths from the Western Pacific and the Bay of Bengal accounted for 26.3% and 73.7%, respectively. At 700 hPa, the paths included the Western Pacific, southwest paths from the Indian Ocean, and westward paths from the Tibetan Plateau, with contributions of 17.1%, 77.9%, and 5.0%, respectively. As the initial height of the moisture trajectory simulation increased, the spatial distribution of the number of trajectories showed a pattern of more in the west and less in the east, and both temperature and specific humidity increased(decreased) during the transport process. [Conclusion] The moisture for the rainfall event in the Dongpu and Dafangying reservoir basins of Hefei City in July 2021 primarily originated from oceanic channels at different height levels, with significant contributions from the Western Pacific, the Bay of Bengal, and the Indian Ocean. At the 850 hPa level, a very strong moisture convergence zone was observed, providing ample moisture for localized heavy rainfall.

Keywords

Dongpu and Dafangying Reservoirs / rainfall / HYSPLIT / water vapor transport / water vapor flux divergence / climate change / spatiotemporal distribution