2021年7月18 -22日， 河南中北部出现历史罕见特大暴雨（“21·7”特大暴雨）， 众多学者已有分析和研究。受系统北上影响， 20 -22日位于太行山中段的河北省中南部也出现区域性大暴雨。本文利用0.25°×0.25°逐小时ERA5再分析资料和2508个地面加密自动站分钟资料、 多普勒天气雷达、 风廓线雷达、 L波段探空、 地基GPS水汽等多源高时空分辨率观测资料， 对太行山中段区域大暴雨演变特征及暴雨落区成因进行分析， 结果表明： （1）强降水主要影响系统为副热带高压、 高空涡、 切变线、 低空急流， “烟花”和“查帕卡”双台风远距离输送也是有利的环流背景， 大气环流稳定和低空偏东风长时间维持是降水的主要成因。（2）近乎南北向地面辐合线、 地面露点温度锋区、 ≥30 dBz雷达强回波带、 小时降水量≥10 mm短时强降水带位置吻合， 且稳定维持在太行山东麓， 位置少动且持续时间长； 强降水阶段， 低层偏东风分量增大， 且最大东风出现高度降低， 最大东风分量为8~11.1 m·s^-1， 最大东风出现的高度最低为510 m； 低空急流最大高度510~2310 m， 最大低空急流指数33.1×10^-3 s^-1， 0~1 km和0~3 km垂直风切变最大分别为11.9 m·s^-1和 16.9 m·s^-1， 偏东风表现为迎风坡水平辐合， 对太行山东麓降水产生明显增幅作用。（3）深厚湿层从地面持续到400 hPa， 降水过程中抬升凝结高度接近地表， 降水前期对流有效位能1925.5 J·kg^-1； 强降水阶段GPS水汽总量处于50 mm以上的高值阶段， 高值开始时间提前于降水5~6 h； 西部山区中低层水汽通量大值区维持时间长达10 h， 水汽辐合西部明显高于东部， 强降水出现在西部山区呈带状分布。（4）雷达回波质心低， 30 dBz以上的强回波在西部山区持续时间长达20 h， 具有列车效应和暖云降水特点。

"21·7" severe torrential rain occurred in Middle-North of Henan Province from 18 to 22 July 2021， which has been studied by many scholars.Affected by the northward movement of the weather systems in “21·7” torrential rain， a regional heavy rainstorm occurred subsequently in the middle section of Taihang Mountains from 20 to 22 July.Based on 0.25°×0.25° hourly ERA5 reanalysis data and multi-source high-resolution observation data from 2508 ground dense automatic weather stations， Doppler radar， wind profile radar， L-band radiosonde， ground-based GPS water vapor and so on， the characteristics and synoptic analysis of the heavy rain in the middle section of Taihang Mountains from 20 to 22 July 2021 were analyzed.The results show that： （1） The main weather systems were subtropical high， upper-tropospheric low vortex， shear line， low-level jet， moreover the long-distance water vapor transport of double typhoon of "In-Fa" and "Cempaka" was favorable to the heavy rain.The main synoptic background was stable atmospheric circulation and long-term maintenance of low-level easterly wind.（2） The locations of surface convergence line， surface dew point temperature front area， the strong echo area with reflectivity factor greater than 30 dBz， and short-term heavy precipitation zone of hourly precipitation greater than 10 mm were nearly consistent and stably maintained at the eastern foot of Taihang Mountains with less movement and long duration.During heavy precipitation phases， the easterly component of low-level winds increased， and the maximum height of east wind decreased.Farther， the maximum easterly component was 8 to 11 m·s^-1， the maximum height of east wind was 510 m.The maximum height of low-level easterly jet was 510 m to 2310 m， the maximum low-level jet index was 33.1×10^-3 s^-1； The maximum vertical wind shear of 0~1 km and 0~3 km were 11.9 m·s^-1 and 16.9 m·s^-1 respectively.The easterly wind and Taihang Mountains made a horizontal convergence on windward slope， also the obvious terrain effect induced the increase of precipitation.（3） The deep wet layer extended from the ground to 400 hPa.During the precipitation process， the condensation height was close to the surface.The convective effective potential energy in the early stage of precipitation was 1925.5 J·kg^-1.In the stage of heavy precipitation， when the GPS water vapor was higher than 50 mm， the start time of high water vapor was 5~6 hours ahead of the precipitation.The large value of water vapor flux of the middle and lower layers in the western mountainous area lasted for more than 10 hours， and the water vapor convergence was significantly higher than that in the East.Heavy precipitation presented as a band shape in front of Taihang Mountains.（4） The centroid of radar echo was low， and the strong echo area with reflectivity factor greater than 30 dBz lasted for 20 hours， the characteristics of train effect and warm-cloud precipitation were obvious in the western mountainous area.