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“23·7”华北特大暴雨过程的基本特征与成因初探

Analysis on the characteristics and causes of the "23·7" torrential rainfall event in North China

  • 摘要: 2023年7月29日08时—8月2日08时(北京时),华北地区出现历史罕见的特大暴雨,造成严重灾害。利用常规高空和地面、FY-4A卫星红外云顶亮温(TBB)等观测资料以及ERA5再分析资料对此次天气过程的降水实况特征和成因进行了分析。结果表明:此次过程的累计降水量、降水持续时间等在华北地区均具有显著极端性;北京西部、河北中部和西南部等多地出现特大暴雨,累计降水量超过400 mm,局地达1 000 mm以上,降水极值多分布于太行山东麓;根据FY-4A卫星TBB、逐小时降水量和主要影响系统的演变特征,强降水可分为三个阶段,第一阶段降水范围和累计降水量最大,第二阶段对流性最强,多站出现100 mm·h-1以上的极端强降水。此次特大暴雨过程发生在台风残涡北上停滞的稳定环流背景下,台风“杜苏芮”和“卡努”提供了持续而充沛的水汽和能量,高空辐散与低层强辐合提供了稳定而强大的动力条件,偏东气流在太行山东麓强迫抬升,使降水增幅并持续。

     

    Abstract: An historically heavy rainfall event occurred in North China from 29 July to 1 August in 2023, causing serious disasters. In this study, the precipitation characteristics and causes of this heavy rainfall event was investigated utilizing various observational data from such as conventional surface and upper air data, FY-4A satellite TBB, and ERA5 reanalysis data. The results are as follows. This event exhibited significant extremity in North China in terms of many aspects, such as the duration and accumulated precipitation. Torrential rainfall occurred in many regions, including western Beijing, central and southwest Hebei, with the total accumulated precipitation amount of exceeding 400 mm and even greater than 1 000 mm locally. The extreme precipitation was mostly distributed in the eastern foot of the Taihang Mountains. Based on the evolution characteristics of FY-4A satellite TBB, hourly precipitation, and major impact systems, severe precipitation can be divided into three stages. The first stage had the largest precipitation coverage and accumulated precipitation, while the second stage had the strongest convection with extreme hourly precipitation of over 100 mm·h-1 occurring at several stations. The extremely heavy rainfall event took place under the background of stable circulation with Typhoon residual vortex stagnating after its moving northward. Typhoons "Doksuri" and "Khanun" provided continuous and abundant water vapor and energy. Obvious upper-level divergence and low-level strong convergence provided stable and powerful dynamic conditions. Due to the forced uplift of the eastward airflow along the eastern foothills of the Taihang Mountains, precipitation was increased and sustained.

     

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