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沙颍河流域不同短历时极端降水精细特征分析

Analysis of the Detailed Characteristics of Different Short duration Extreme Precipitation Events in the Shaying River Basin

  • 摘要: 利用2013—2022年5—9月沙颍河流域35个国家站和886个区域站逐时降水资料,对1 h、3 h、6 h等3个短历时极端降水的极值、阈值、降水平均强度及频次等进行详细分析。结果表明:(1) 沙颍河流域不同短历时降水极值呈现西部小、北部及东北部和南部大的空间分布特征,历时越长,极值局地性越强。(2) 以99.5%分位数的降水作为短历时极端降水阈值,不同历时极端降水阈值空间分布呈现“西低东高”,历时越长,该特征越明显。(3) 不同短历时极端降水强度和频次空间分布呈现明显的区域差异,其中高强度区集中在沙颍河流域北部嵩山与平原过渡带、南部和东北部的平原地区,高频次区则位于沙颍河流域西部山区,且随历时增加,强度与频次的空间分布不均匀性越显著。(4) 月尺度变化上,短历时极端降水平均强度随历时增加逐渐由7月单峰型(1 h、3 h)演变为7月、9月双峰型(6 h);而频次均为7月单峰型。日变化显示,降水平均强度与频次均呈双峰型,其中主峰在午后至傍晚,次峰在凌晨。强度随历时增加主峰时段后延、次峰时段前移,峰值趋于夜间集中。频次6 h峰值阶段与1 h、3 h呈反向变化,历时越短,日变化越明显,1 h最显著。研究有助于加深对本地不同短历时极端降水过程的理解和提高极端降水预警能力,也为后续短历时极端降水的潜势预报和临近客观预报奠定了数据基础。

     

    Abstract: Using hourly precipitation data from 35 national stations and 886 regional stations in the Shaying River basin from May to September during 2013—2022, a detailed comparison is conducted of the characteristics of extreme precipitation for three short durations (1 h, 3 h and 6 h), including their extremes, thresholds, average precipitation intensities and frequencies. The results are as follows: (1) The spatial distribution of extreme values of short-duration precipitation in the Shaying River Basin shows the characteristics of smaller values in the western part and larger values in the northern, northeastern and southern parts. The longer the duration, the stronger the regional distribution of extreme values becomes. (2) Taking the 99.5th percentile of precipitation as the threshold for short-duration extreme precipitation, the spatial distribution of extreme precipitation thresholds for different durations exhibits a pattern of "lower in the west and higher in the east". This characteristic becomes more pronounced as the duration increases. (3) The spatial distributions of short duration extreme precipitation intensity and frequency exhibit pronounced regional heterogeneity across the basin. High-intensity zones are concentrated in transition areas between Songshan Mountain and the plain in the northern part of the Shaying River Basin, and the plain areas in the southern and northeastern parts of the Shaying River Basin, while high-frequency zones dominate the western mountainous areas of the Shaying River Basin. Notably, spatial inhomogeneity of both intensity and frequency distributions becomes more pronounced with increasing precipitation duration. (4) On the monthly scale, the average intensity of short duration extreme precipitation transitions from a monomodal pattern (peaking in July for 1 h and 3 h durations) to a bimodal pattern (dual peaks in July and September for 6 h duration) with increasing duration, while the frequency consistently exhibits a monomodal concentration in July. Diurnal variation is shown, both intensity and frequency display bimodal variations, characterized by a primary peak (afternoon to evening) and a secondary peak (early morning). The intensity shows a temporal phase shift toward later hours for the primary peak and earlier hours for the secondary peak with prolonged duration, resulting in peak concentration gradually concentrated during nighttime. In contrast, the 6 h precipitation frequency exhibits a reverse pattern in peak phase compared to shorter durations (1 h, 3 h) and shorter durations (notably 1 h) demonstrate more pronounced diurnal variability in frequency, with higher amplitude and stronger day-night contrast. This study significantly enhances the understanding of local short-duration extreme precipitation processes and improves early warning capabilities. Furthermore, it establishes a critical data foundation for subsequent probabilistic forecasting and nowcasting of short-duration extreme precipitation events.

     

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