An extremely heavy rainfall occurred in Henan Province, China, from July 19th to 21st in 2021, with large precipitation, long duration and wide precipitation area. Impact of water vapor transportation from atmospheric river (AR) on the rainfall was studied through reanalysis data and weather research and forecasting (WRF) model. Precipitation reached over 600 mm around Mount Song, which lasted for 48 h. The AR provided sufficient water vapor condition for the long-lasting rainfall. Regional averaged hourly precipitation was positively correlated with the amplitude of Integrated Horizontal Water Vapor Transport (IVT) and negatively correlated with IVT divergence (IVTD). Maximum precipitation regions were consistent with large IVT and IVTD regions. Peaks of IVT and IVTD were advancing of precipitation peak. Precipitation was affected by Mount Song through influencing spatial distribution and vertical structure of ARs and vertical velocity. Orographic lifting and wind converging around Mount Song caused the heavy rainfall in Zhengzhou City on July 20th. Precipitation, large IVT, IVTD and updrafts region located northwesterly of Mount Song in half mountain and without mountain tests. Comparing sensitivity tests with control simulation, air mass transporting by the AR and convective systems slowed down (or stagnated) when met the mountain, resulting in long lasting duration and large precipitation.

中文翻译：

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大气河流和当地地形对河南省“21·7”特大暴雨的影响


2021年7月19日至21日，我国河南省出现一次特大暴雨，雨量大、持续时间长、降水面积广。通过再分析数据和天气研究与预报（WRF）模型，研究了大气河（AR）水汽输送对降雨的影响。嵩山周边降水量达600毫米以上，持续48小时。 AR为此次持久降雨提供了充足的水汽条件。区域平均小时降水量与综合水平水汽输送（IVT）幅度正相关，与IVT散度（IVTD）负相关。最大降水区域与大IVT和IVTD区域一致。 IVT和IVTD峰值均较降水峰值提前。嵩山通过影响ARs的空间分布和垂直结构以及垂直速度来影响降水量。 7月20日，受地形抬升和嵩山周围风力汇聚影响，郑州市出现强降雨。降水、大IVT、IVTD和上升气流区位于嵩山西北半山区，未进行山地测试。将灵敏度测试与控制模拟进行比较，AR和对流系统的气团输送在遇到山脉时减慢（或停滞），导致持续时间长和降水量大。