Analysis of short-term heavy rainfall change trend and its causes in Jiangxi Province from April to September during 1979-2019

doi:10.11755/j.issn.1006-7639-2025-04-0595

Abstract

Abstract:

The variation trend and potential causes of short-term heavy rainfall (STHR) in Jiangxi Province were studied to enhance the forecasting and early-warning capabilities about extreme precipitation events, particularly for STHR. Baud on hourly precipitation data from 84 national meteorological stations in Jiangxi Province during 1979-2019 and ERA5 atmospheric reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF), anomaly normalization, linear tendency estimation, the Mann-Kendall test, and correlation analysis were employed to investigate the variation trend of STHR in Jiangxi Province and its potential influencing factors. The results are as follows: (1) STHR in Jiangxi Province exhibits distinct seasonal characteristics. From April to September, the frequency and proportion of such events account for 95.7% and 92.4% of the annual totals, respectively. (2) According to the hourly rainfall（R）, STHR was classified into three levels: 20≤R<30 mm, 30≤R<50 mm, and R≥50 mm, referred to as levels I, Ⅱ, and Ⅲ, respectively. The spatial distribution of levels I and Ⅱ shows higher frequencies in the eastern regions than in the western regions, with great activity observed over mountainous terrain than over plains and basins. By contrast, level III STHR exhibits no distinct spatial pattern. On the whole, the annual frequency and annual proportion of STHR across all levels show an increasing trend, with a significant shift observed at the onset of the 21st century. (3) The anomaly of high precipitable water vapor and the anomaly of low-level atmospheric pseudo-equivalent potential temperature were significantly positively correlated with the annual mean frequency anomaly and annual proportion anomaly of STHR in Jiangxi Province. Moreover, the correlation coefficient gradually decreases as the intensity level of STHR increases. Composite analysis of strong and weak STHR years indicate that when the Western Pacific Subtropical High and the Ural High are abnormally strong, accompanied by an anomalously strong low-level southwesterly flow, the frequency of STHR events in Jiangxi Province increases; conversely, the opposite circulation configuration leads to fewer STHR occurrences.

Key words: short-term heavy rainfall, precipitable water vapor, pseudo-equivalent potential temperature, circulation background

摘要：

研究江西省短时强降水的变化趋势及其可能成因，以提升短时强降水等极端降水事件的预报预警能力。本文基于1979—2019年江西省84个国家气象观测站的小时降水资料及欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts，ECMWF）ERA5大气再分析资料，采用距平化处理、线性倾向估计、Mann-Kendall检验和相关性分析等方法，探究江西省短时强降水的变化趋势及其可能的影响因素。结果表明：（1）江西省短时强降水具有显著的季节性特征，4—9月的短时强降水频次和占比分别为全年的95.7%和92.4%。（2）根据小时雨量（R），将短时强降水分为20≤R<30 mm（I级）、30≤R<50 mm（Ⅱ级）、R≥50 mm（Ⅲ级）3个级别。其中，I、II级短时强降水的空间分布整体表现为东多西少，山区多于平原和盆地，而III级短时强降水无明显空间分布特征。所有级别的短时强降水年均频次和年占比均呈增长趋势，且在21世纪初发生突变。（3）江西省大气可降水量高值频次距平、低层大气假相当位温距平与江西省短时强降水年均频次距平及其年占比距平呈显著正相关，且相关系数随着短时强降水量级的增加而逐渐降低。短时强降水高、低频年大气环流分析表明，当西太平洋副热带高压和乌拉尔高压异常偏强，并伴随低层异常强盛西南气流时，江西省短时强降水事件偏多，反之则偏少。

关键词: 短时强降水, 大气可降水量, 假相当位温, 环流背景

CLC Number:

P467

LI Zhehua, XIAO An, TU Manhong, WU Wenxin. Analysis of short-term heavy rainfall change trend and its causes in Jiangxi Province from April to September during 1979-2019[J]. Journal of Arid Meteorology, 2025, 43(4): 595-606.

李浙华, 肖安, 涂满红, 吴文心. 1979—2019年4—9月江西省短时强降水变化趋势及成因分析[J]. 干旱气象, 2025, 43(4): 595-606.

Figures/Tables 10

Fig.1 Spatial distribution of national meteorological stations （black dots） and altitude （the color shaded， Unit： m） in Jiangxi Province

Fig.2 Monthly average frequency and monthly proportion distribution of short-time heavy rainfall in Jiangxi Province during 1979-2019

Fig.3 The inter-annual variation （a， c， e） and M-K mutation tests （b， d， f） of Ⅰ （a， b）， Ⅱ （c， d）， Ⅲ （e， f） level short-time heavy rainfall frequency in Jiangxi Province from April to September during 1979-2019

Fig.4 The inter-annual variation （a， c， e） and M-K mutation tests （b， d， f） of Ⅰ （a， b）， Ⅱ （c， d）， Ⅲ （e， f） level short-time heavy rainfall proportion in Jiangxi Province from April to September during 1979-2019

Fig.5 Spatial distribution of annual average precipitation （a）， frequency （b）， and proportion （c） of short-time heavy rainfall， and the annual average frequency （d， e， f） and annual proportion （g， h， i） of Ⅰ （d， g）， Ⅱ （e， h） and Ⅲ （f， i） level short-term heavy rainfall in Jiangxi Province from April to September during 1979-2019

Fig.6 Inter-annual variation of PWV （a）， frequency of high PWV （b）， and frequency of low PWV （c） in Jiangxi Province from April to September during 1979-2019

Fig.7 Correlation coefficients between frequency anomalies of high PWV and the average annual frequency anomaly and annual proportion anomaly of short-term heavy rainfall with different levels in Jiangxi Province from April to September during 1979-2019

Fig.8 Inter-annual variation of atmospheric θse at different pressure levels in Jiangxi Province from April to September during 1979-2019

Fig.9 Correlation coefficients between θse anomalies at different pressure levels and annual frequency anomalies and annual proportion anomalies of short-term heavy rainfall with different levels in Jiangxi Province from April to September during 1979-2019

Fig.10 The 500 hPa geopotential height anomalies （Unit： dagpm）（a， c） and 850 hPa wind anomalies （Unit： m·s-1）（b， d） of high （a， b） and low （c， d） frequency years of short-term heavy rainfall， the difference of composite 500 hPa geopotential height （e， Unit： dagpm） and 850 hPa wind field （f， Unit： m·s-1） between the high and low frequency years of short-time heavy rainfall in Jiangxi Province （Letters G and D represent high pressure and low pressure respectively， green shading denotes 95% confidence level， the area surrounded by the red line represents Jiangxi Province）

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