Numerical Study on the Effects of Intraseasonal Oscillations for a Persistent Drought and Hot Event in South China Summer 2022

Abstract

From 19 July 2022 to 31 August 2022, a rare persistent drought and heat event occurred in the middle of the Yangtze River basin (MYRB). Normalized difference vegetation Index (NDVI) over 25% of the area decreased more than 0.05 compared with the climatology, causing extremely agricultural drought disaster and economic losses to China. Previous studies have shown that the occurrence of compound drought and heat events (CDHEs) in the MYRB was associated with intra-seasonal oscillations (ISOs) from different latitudes. Nevertheless, what was the role of ISOs at different latitudes in the formation of the CDHE? To address this question, this paper designed a numerical simulation experiment of partial lateral forcing to investigate the changes in meteorological elements by removing the signals of ISOs on different lateral boundaries. We found that the wave series formed in the upper troposphere at 200 hPa played a significant role in the occurrence of the CDHE in the northern part of the MYRB in this progress. It was found that the ISO component of the northern boundary caused the mean temperature to rise by 2.4 °C and aggravated the drought in 53.7% of the region. On the other hand, the anticyclone anomaly in the lower troposphere at 800 hPa had a continuous impact on the southern and eastern boundaries. It was found that the ISO component of these two boundaries can increase the average temperature by 1.93 °C in the MYRB and intensify the drought in 49.7% of the area. In the developing period of the CDHE, the South Asian high and the Western North Pacific subtropical high were coupled with each other and jointly controlled the MYRB, so that the significant positive geopotential height anomaly stayed above the MYRB for a long time, which was conducive to the development of local subsidence. The results of this paper will help to better understand the formation mechanism of CDHEs in the MYRB and assist meteorologists to prevent and forecast the occurrence of CDHEs in advance.

Was the 2022 drought in the Yangtze River Basin, China more severe than other typical drought events by considering the natural characteristics and the actual impacts?

“…In 2022, the South Asian high pressure and Western North Pacific subtropical high pressure were coupled with each other and jointly controlled the middle reaches of the YRB, so the significant positive geopotential height anomaly remained above the middle reaches of the YRB for a long time, which was conducive to the development of local subsidence (Qin et al, 2023). Hua et al (2023) (Villafuerte and Matsumoto, 2015;Peng et al, 2018).…”

Analysis of drought characteristics and comparison of historical typical years with 2022 drought in the Yangtze River Basin

“…As for other reasons that caused the 2022 drought in YRB, previous research has attributed it to the intra-seasonal oscillations from different latitudes (Qin et al 2023), the anomalously strong westward extension of the western Pacific subtropical high pressure, and the anomalous anticyclonic circulation in the mid-upper troposphere over northern central and eastern China (Wang et al 2023). In addition, the higher water demand also exacerbated the drought situation in this basin.…”

“…As the drought progressed, it triggered a cascade of effects, with over 44.21 thousand km 2 cultivated land reducing grain production, and 4.99 million people and 920 thousand large livestock facing difficulties in drinking water due to drought (Xia et al 2022). Some scholars have also conducted analysis and research on this drought event (Liu et al 2023a;Qin et al 2023). Lv et al (2022).…”

Analysis of drought characteristics and comparison of historical typical years with 2022 drought in the Yangtze River Basin

“…As the drought progressed, it triggered a cascade of effects, with over 44.21 thousand km 2 cultivated land reducing grain production, and 4.99 million people and 920 thousand large livestock facing difficulties in drinking water due to drought (Xia et al 2022). Some scholars have also conducted analysis and research on this drought event (Liu et al 2023a;Qin et al 2023). Lv et al (2022).…”