Extreme Rainfall Simulations with Changing Resolution of Orography Based on the Yin-He Global Spectrum Model: A Case Study of the Zhengzhou 20·7 Extreme Rainfall Event

Abstract

In recent years, the study of numerical weather prediction (NWP) in complex orographic areas has attracted a great deal of attention. Complex orography plays an important role in the occurrence and development of extreme rainfall events. In this study, the Yin–He Global Spectrum Model (YHGSM) was used, and the wave number truncation method was employed to decompose the orographic data to different resolutions. The obtained orographic data with different resolutions were used to simulate the extreme rainfall in Zhengzhou, Henan Province, China, to discuss the degree of influence and mechanism of the different orographic resolutions on the extreme rainfall. The results show that the simulation results of the YHGSM with high-resolution orography are better than those of the low-resolution orography in terms of the rainfall intensity and range. When the rainfall intensity is higher, the results of the low-resolution orography simulated the rainfall range of big heavy rainfall better. The orography mainly affected the rainfall by affecting the velocity of the updraft, but it had a limited influence on the maximum height that the updraft could reach. A strong updraft is one of the key factors leading to extreme rainfall in Henan Province. When the orographic resolution changes, the sensitivity of the vertical velocity of the updraft to the orographic resolution is the greatest, the sensitivity of the upper-air divergence and low-level vorticity to the orographic resolution is lower than that of the vertical velocity. In conclusion, the high-resolution orography is helpful in improving the model’s prediction of extreme rainfall, and when predicting extreme rainfall in complex orographic areas, forecasters may need to artificially increase rainfall based on model results.

Orographic Construction of a Numerical Weather Prediction Spectral Model Based on ASTER Data and Its Application to Simulation of the Henan 20·7 Extreme Rainfall Event

“…Exp0 was the control experiment, in which the model's original orography was used. Wang et al [36] used the same configuration as exp0 when studying the effect of orographic resolution on NWP model simulations. They found that the YHGSM performed best using the orography of exp0.…”

“…There are 145 meteorological observation stations in the main precipitation area. Among them, Zhengzhou Station had an hourly rainfall of 201.9 mm at around 9:00 on 20 July 2021, setting a record in China and causing great damage to the environment and people [36]. Figure 5 shows hourly changes in total rainfall in the main precipitation area.…”

Subseasonal Predictability of the July 2021 Extreme Rainfall Event Over Henan China in S2S Operational Models

“…Both strong ascending motion and abundant moisture supply were responsible for the occurrence of extreme flooding (Fu et al., 2022; S. Zhang et al., 2022). The regional numerical model, to some extent, can reproduce synoptic systems and extreme rainfall (X. Y. Wang et al., 2022; Yin et al., 2022). However, nearly all the operational models underpredicted the rainfall intensity (Shi et al., 2021; Q. J. Huang et al., 2022; X. J. Wang et al., 2022; H. X. Xu et al., 2022).…”