Evolution and prediction of the extreme rainstorm event in July 2021 in Henan province, China

Abstract

The Once‐in‐a‐Century extreme rainstorm event caused severe floods over Henan province during July 18–21, 2021, which resulted in large casualty and property losses. Although the rainstorm event occurred in Henan after July 18, the excessive rainfall had occurred to the east of Henan before July 18, with the 4‐day accumulated rainfall exceeding +130 mm during July 14–17, 2021. How the rainfall evolving westward and intensifying after July 18 remained a puzzle, which is the focus of this study. The prerainstorm stage (July 14–17) was related to the South Asian High (SAH) extending eastward and the western Pacific subtropical high (WPSH) extending northwestward, and a low vortex between the SAH and WPSH caused above‐normal rainfall to the east of Henan. The rainstorm stage (July 18–21) was associated with an inverted trough and excessive southerly and southeasterly water vapor transportation above Henan, which resulted from the combined effects of a deep trough in the upper troposphere and typhoon activities. Additionally, three subseasonal forecasting systems predicted this rainstorm event 3 days in advance, with the European Center for Medium Range Weather Forecasts (ECMWF) performing the best, which was related to a better prediction of the inverted trough and the water vapor transportation in the middle‐lower troposphere. These results advance our understanding of the extreme rainstorm event in July 2021 in Henan.

Urban Flood Loss Assessment and Index Insurance Compensation Estimation by Integrating Remote Sensing and Rainfall Multi-Source Data: A Case Study of the 2021 Henan Rainstorm

“…Therefore, multidimensional remote sensing was used to decode the flood inundation extent of the extraordinary rainstorm in Henan Province (Figure 4), and the disaster losses of each remote sensing pixel were calculated. As shown in Figure 4, the affected pixels were mainly distributed in areas of heavy rainfall, such as Zhengzhou, Luoyang, Kaifeng and other cities, which is consistent with the findings of existing studies [8,53]. Among them, Zhengzhou City was more severely affected by flooding and inundation, and the heavy rainfall and flooding made the extent of water bodies after the disaster significantly larger than the water body information before the disaster.…”

“…Henan Province (Figure 1) (110 • 21 -116 • 39 E, 31 • 23 -36 • 22 N) is located in eastcentral China and the middle and lower reaches of the Yellow River. The topography is complex, characterized by a high west and low east, surrounded by mountains in the north, west and south and plains in the east [8]. The total area under its jurisdiction is 167,000 km 2 [50].…”

“…Floods are one of the most severe natural disasters worldwide [1], often causing huge economic losses and serious human casualties [2,3]. In the context of climate warming, extreme rainstorms are becoming more frequent [4] and more prone to causing widespread flooding [5], severely constraining sustainable socio-economic development, for example, floods in Thailand in 2011 [6], flooding along the Elbe River in Germany in 2013 [7], heavy rainfall across central Europe in 2021 [2], an extraordinary rainstorm in Henan in 2021 [8][9][10] and floods in Pakistan in 2022 [11]. Currently, in response to natural disasters, government departments use post-disaster relief to provide assistance [12], with a huge financial burden [13].…”