Primary characteristics of the extreme heavy rainfall event over Henan in July 2021

Abstract

During mid‐July 2021, an extreme heavy rainfall event (HRE) occurred in Henan Province (hereafter “21.7” HRE), with extreme hourly precipitation of 201.9 mm appearing at Zhengzhou station. Our preliminary analyses of the “21.7” HRE using the observations and ECMWF (European Centre for Medium‐Range Weather Forecasts) ERA5 reanalysis data, reached the following conclusions. Favorable configurations of various synoptic weather systems (e.g., strong upper‐level high‐pressure ridge, intense middle‐level low‐pressure trough) acted as crucial background conditions for the occurrence of the “21.7” HRE. A 21‐h long‐lived mesoscale convective vortex (MCV), mainly located in the middle and lower troposphere west of Zhengzhou city, was a key system that produced the extreme hourly rainfall of 201.9 mm·h−1. The MCV's development/sustainment was dominated by the vertical transport of cyclonic vorticity and tilting, as well as the horizontal import of cyclonic vorticity to the vortex's key region. In contrast, the divergence‐related vertical shrinking was the most detrimental factor. Lagrangian moisture transport analysis showed that moisture for the extreme heavy rainfall in Zhengzhou on July 20 mainly came from levels below 2200 m, driven by airflows on the peripheries of tropical cyclones IN‐FA and CEMPAKA. To enhance the understanding of “21.7” HRE, we suggest more in‐depth investigations in the future.

Response of remote water vapor transport to large topographic effects and the multi-scale system during the “7.20” rainstorm event in Henan Province, China

“…The BT dominated the remote moisture transport from the South China Sea and the Northwest Pacific Ocean, in which typhoon In-fa played a major role. This impact of BT on large-scale circulation has been demonstrated in moisture sources and moisture proportions of different trajectories experiments (Nie and Sun, 2022;Sun et al, 2023). Compared with the general overview of the BT effect above, our conclusions highlight the specific mechanism of the Western Pacific typhoon in BT.…”

“…The terrestrial and oceanic moisture over southern China-western North Pacific was both crucial for the extreme precipitation event over Henan (Nie and Sun, 2022). The main moisture transport was driven by airflows on the peripheries of binary tropical typhoon (BT) In-fa and Cempaka (Deng et al, 2022;Sun et al, 2023). The event produced well-organized mesoscale convective systems whose unique dynamic structure contributes significantly to record-high hourly rainfall (Yin et al, 2021).…”

ZDR Backwards Arc: Evidence of Multi‐Directional Size Sorting in the Storm Producing 201.9 mm Hourly Rainfall

“…On 20 July 2021, an unprecedented rainfall storm pouring record-breaking hourly rainfall of 201.9 mm hit urban Zhengzhou and caused tremendous losses. This event took place under favorable synoptic conditions (Sun, Fu, et al, 2023;J. Xu et al, 2022;S.…”

“…On 20 July 2021, an unprecedented rainfall storm pouring record‐breaking hourly rainfall of 201.9 mm hit urban Zhengzhou and caused tremendous losses. This event took place under favorable synoptic conditions (Sun, Fu, et al., 2023; J. Xu et al., 2022; S. Zhang et al., 2022), including the weak Huang‐Huai cyclone, the western Pacific subtropical high, the deep Tibetan high, and Typhoons In‐Fa and Cempaka (Yin et al., 2022). The meso‐ β ‐scale low pressure system developed from southwest of Zhengzhou was conducive to the intensification of the rainstorm (Sun, Li, et al., 2023).…”

Quantitative attribution of historical anthropogenic warming on the extreme rainfall event over Henan in July 2021

“…Previous studies of the '21•7' HNER have mainly focused on synoptic weather systems, such as the upper level high-pressure ridge and mid-level trough (Sun et al 2022), the water vapor channel modulated by the subtropical high and the westerly belt (Gao et al 2022), the persistent double low-level jets (Luo and Du 2022), the impacts of the upper tropospheric cold low (Cai et al 2022), the interactions of binary typhoons Infa (2021) and Cempaka (2021) as well as their remote impact (Xu et al 2023). Besides, the mesoscale convective systems are also of interest, such as the embedded mesoscale vortex (Fu et al 2022), the well-organized meso-γ-scale convective system (Yin et al 2022).…”