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近10 a偏东气流影响下梵净山东侧暴雨时空特征

Spatial-temporal characteristics of rainstorm on the eastern Fanjing Mountain under the influence of easterly airflow in recent ten years

  • 摘要: 受地形和低层偏东气流共同影响,梵净山东侧强降水频发,给当地人民生命财产安全造成严重威胁。利用2014—2023年贵州省铜仁市国家气象站和区域气象站降水观测数据以及ERA5再分析数据,分析低层偏东气流影响下梵净山东侧暴雨(Rainstorm on the eastern Fanjing Mountain under the influence of easterly airflow,RF)的时空特征。结果表明:(1) RF常出现在925 hPa盛行偏东气流背景下,每年发生15次左右,集中在5—9月,6月和8月发生次数最多,其次是7月,6—8月的RF占所有RF事件的65.3%。(2) RF降水具有显著的区域性特征,地形显著影响降水分布,降水量、频率和强度大值中心出现在海拔高度差最大的梵净山东麓,其次是梵净山东北侧开口朝向东北方向的喇叭口地形狭窄处。大暴雨以上量级的降水频率和强度分布表明梵净山东侧比东北侧更易发生较大范围的极端暴雨。(3) RF降水量、强度和频率均呈现白天低、夜间高的日变化特征,降水强度显著影响降水量日变化,降水量在08时的主峰值受5月和6月降水强度的影响,22时左右的次峰值受8月降水强度的影响,而15时左右的第三峰值受5月和7月降水强度的影响。同时5—9月各月在22时左右均具有降水量大、强度较强的特征。(4) 6月和7月的RF具有极端性,持续时间达6~7 h,8月的RF持续时间为4 h左右。

     

    Abstract: The frequent heavy rainfall on the eastern Fanjing Mountain due to the combined influence of topography and easterly airflow at low-level have bad significant effects on the lives and property of local people. This paper focuses on revealing the spatial-temporal distribution characteristics of rainstorm on the eastern Fanjing Mountain under the influence of easterly airflow (RF) at low-level based on the precipitation observation data from the national and regional automatic weather stations in Tongren City,Guizhou Province, as well as ERA5 reanalysis data during 2014-2023.The results are as follows. (1) RF often occurs under the background of prevailing easterly airflow at 925hPa,with about 15 occurrences per year, and it is concentrated from May to September of the year with the most appearance occurring in June and August, followed by July. The RF events from June to August account for 65.3% of all RF events. (2) The RF is affected by topography significantly with regional characteristics. The maximum of precipitation amount, frequency, and intensity are located at the eastern foot of Fanjing Mountain where the altitude difference is the greatest, followed by the narrow trumpet-shaped topography facing northeastward at the northeastern Fanjing Mountain. Also, it is more likely to occur that widespread extreme rainstorm on the eastern Fanjing Mountain than that on the northeastern Fanjing Mountain according to the distribution of precipitation frequency and intensity above the downpour. (3) RF precipitation amount, intensity, and frequency all show a diurnal variation pattern of being low value during the daytime and high value at nighttime. And the diurnal variation of precipitation amount is mainly affected by the precipitation intensity, because the main peak value of precipitation amount around 08:00 is contributed by the precipitation intensity in May and June, meanwhile the secondary (third) peak value of precipitation amount around 22:00 (15:00) is contributed by the precipitation intensity in August (May and July). Furthermore, it is obvious to see that the characteristics of larger precipitation aomunt and stronger precipitation intensity from May to September around 22:00. (4) It is clear that the RF in June and July lasting 6~7 h is extreme, while RF lasting 4 h is prone to occur in August.

     

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