2010-2019年海河流域暖季极端小时降水特征分析

Analysis on Characteristics of Extreme Hourly Precipitation in Warm Season in the Haihe River Basin from 2010 to 2019

利用海河流域4517个气象站(含国家基本气象站和区域自动气象站)逐小时降水量资料和ERA-5再分析资料,采用百分位法对2010-2019年海河流域的暖季极端小时降水(Extreme Hourly Precipitation, EHP)的阈值、频次、时空变化及天气型进行统计分析。结果表明:(1)海河流域所有站点小时降水99.9%分位数的平均值为45.6 mm·h^(-1),且有67%的站点小时降水的99.9%分位数对应雨强大于45.0 mm·h^(-1),因此把45.0 mm·h^(-1)作为海河流域极端小时降水的阈值。(2)海河流域的EHP频次空间分布与地理位置及地形特征密切相关,表现为平原的频次大于山区的、山前的大于山上的,随海拔呈现先升后降趋势,在(450,500] m出现海河流域EHP频次的峰值,之后呈现波动减少的趋势。(3)极端小时降水的频次年际变化以2016年为分界点,表现为“先增后减”的趋势,强度在2012年和2016年分别出现2次高点;每年EHP集中出现在7-8月,平均强度大于60 mm·h^(-1),出现频次为全年的78.6%;频次和强度的日变化均表现为“双峰型”,峰值出现在午后和凌晨,其中午后峰值更为显著。(4)对不同天气类型的EHP频次和强度的统计结果表明,7-8月EHP事件中副高边缘类占比较大;EHP频次的午后峰值主要由低涡切变和低槽引起,凌晨峰值则与副高边缘类密切相关;低涡切变类的EHP中位数强度最大,低槽类的强度最小。

Based on the hourly precipitation data from 4517 meteorological stations(national basic weather station and regional automatic weather station)in Haihe River Basin and the ERA-5 reanalysis data,this paper statistically analyzes the threshold,frequency,spatio-temporal changes and weather patterns of extreme hourly precipitation(EHP)in the warm season in Haihe River Basin from 2010 to 2019 by means of the percentile method.The results show that:(1)The average value of 99.9%quantile of hourly rainfall intensity is 45.6 mm·h^(-1) and the 99.9%quantile of hourly rainfall intensity in 67%of the sites exceeds 45.0 mm·h^(-1).Therefore,the value 45.0 mm·h^(-1) is taken as the threshold of EHP in Haihe River Basin.(2)Spatial distribution of EHP frequency in Haihe River Basin is closely related to geographical location and topographical features.The EHP frequency in the plain areas is higher than in the mountain,and that in front of mountains is higher than that on mountains.Along the altitude,the EHP frequency increases first and then decreases,and its peak value tends to appear at the altitude of(450,500]m in Haihe River Basin.After that,there is a trend of decreasing volatility.(3)The inter-annual variation of the EHP frequency firstly increases and then decreases with the year of 2016 as the demarcation point.Two peaks of EHP intensity appear in 2012 and 2016,respectively.EHP is mainly concentrated in July and August every year,with an average intensity of more than 60 mm·h^(-1) and a frequency of 78.6%of the whole year.The diurnal variations of frequency and intensity show a double-peak pattern,and the peaks are observed in the afternoon and the early morning,especially after the noon time.(4)The statistical results of EHP frequency and intensity of different weather patterns indicate that the proportion of edge classes of subtropical high in EHP events from July to August is relatively large.The peak of EHP frequency in the afternoon is mainly caused by low vortex,shear and low trough,and EHP in the early morning is closely associated with the subtropical high edge class.The maximum intensity of median of EHP belongs to vortex shear type,while the minimum intensity of median of EHP is the trough type.