User:甘大面/2023 Beijing flood

On the evening of July 29, 2023, heavy rain occurred in the Beijing-Tianjin-Hebei region of China, and it is still ongoing. Many provinces and cities in mainland China have been affected by the heavy rain, with Beijing and surrounding areas experiencing the largest rainfall in 11 years. As of August 1, the heavy rain has resulted in 20 deaths, 27 missing persons, and 4,673 people affected. The amount of rainfall recorded by instruments in the Beijing area during this rainfall process is the highest on record in the past 140 years.

Weather warning
On the morning of July 28, 2023, Super Typhoon Doksuri made landfall along the coast of Quanzhou, Fujian Province in China. Later that afternoon, China's National Meteorological Center issued a red alert, the highest level warning, for heavy rainfall. This was only the second time a red rainfall warning had been issued since the warning system was formally implemented in 2010. The first time was on September 29, 2011. At that time, forecasts predicted heavy to torrential rains in parts of Hebei Province, Beijing, Tianjin, as well as some areas of Shanxi, Henan and Shandong Provinces. Some areas across Beijing, Tianjin and Hebei were even expected to see extreme torrential rains, with rainfall amounts reaching 200-450 mm.

At 11am on July 29, 2023, the Hebei Provincial Meteorological Bureau upgraded its warning to a red alert for torrential rains. It was forecasted that from July 29 to 31, there would be a continuous period of heavy rainfall across the province, with torrential rains to extremely torrential rains (accumulations of 60-200mm) in most areas. Some parts of Baoding, Xiong'an New Area, Shijiazhuang, Xingtai, and Handan were expected to see especially torrential rains (250-450mm), with local accumulations potentially reaching more than 600mm. At 5:30pm, the Beijing Meteorological Bureau upgraded its warning to a red alert for torrential rains. It was forecasted that from the evening of July 29 to the evening of August 1, Beijing would experience heavy torrential rains, with extremely torrential rains in western and southern parts of the city. At 11am on July 31, it was predicted that from noon to 2pm on July 31, the Danshi River section in Fangshan District would see floods reaching the red alert criteria.

On August 1, 2023, in response to the weakening rain in Beijing, the Beijing Meteorological Bureau downgraded the alert to a yellow warning for torrential rains. .

On August 2, 2023, at 7:30am, the Beijing Meteorological Bureau lifted the yellow torrential rain warning. At the same time, at 6:15am, it lifted the yellow thunderstorm warning. At 7:10am, the Hebei Provincial Meteorological Bureau lifted the torrential rain warning. As the rain band moved northward, Heilongjiang Province was affected by heavy rainfall. At 9:25am, the provincial meteorological bureau issued a red alert for torrential rains, forecasting that from August 2 to 4, the areas in southern Heilongjiang that will see larger rainfall will highly overlap with areas that have already seen heavy rainfall previously, leading to high risks of secondary disasters. At 3pm on August 1, the Office of the Provincial Flood Control and Drought Relief Headquarters, Heilongjiang Provincial Department of Water Resources, and Heilongjiang Provincial Meteorological Bureau jointly issued a meteorological risk warning for floods in small and medium-sized rivers. From 8pm on August 1 to 8pm on August 5, there will be high risks (orange alert) of floods in small and medium-sized rivers across all districts of Harbin and Mudanjiang. Zhaodong, Lanxi, Qing'an, and Tieli will see relatively high risks (yellow alert) of such floods, while Zhalantun, Longjiang, Gannan, and Fuyu will see risks (blue alert) of small and medium river floods.

Rainfall and Flooding
From 8pm on July 29 to 8am on July 31, the average rainfall across Beijing was 140.7mm, with an average of 143.5mm in the urban area, 298.4mm in Fangshan District, and 277.9mm in Mentougou District. The maximum rainfall occurred in Fangshan Xincun at 500.4mm. The maximum hourly rainfall intensity occurred in Panggezhuang Town, Daxing District, from 07:00 to 08:00 on July 31 at 65.8mm/hour.

The Beijing Meteorological Bureau said that from 8pm on July 29 to 7am on August 2, the maximum rainfall recorded during this rainstorm weather process occurred at Wangjiayuan Reservoir in Changping at 744.8mm. This broke the previous heavy rainfall records of 609mm on July 23, 1891 and 519mm on July 21, 2012. The average rainfall across the city was 276.5mm, with an average of 244.9mm in the urban area, 461.4mm in the southwest, 272mm in the northwest, 226.9mm in the southeast, and 198.1mm in the northeast. The maximum urban rainfall occurred in Qianling Mountain, Fengtai at 603.6mm. The maximum rainfall across the entire city occurred at Wangjiayuan Reservoir, Changping at 744.8mm. The maximum hourly precipitation intensity was 111.8mm/hour in Qianling Mountain, Fengtai (from 10:00 to 11:00 on July 31).

According to analysis on Sina Weibo by "Chinese Weather Enthusiasts", the cause of this torrential rain was the collision of a large typhoon with the mountains in North China, resulting in extremely severe consequences. In addition to the influence of Typhoon Dousuri's residual circulation, Typhoon Kanu in the northwest Pacific transported moisture, causing increased moisture in the North China Plain and intensifying this torrential rain. The torrential rains would not weaken until Dousuri's residual circulation completely dissipated. Chief forecaster of China Meteorological Administration Ma Xuekuan admitted this was "extremely rare" and there are five aspects reflecting the extremity of this rainfall: long duration of heavy rainfall, large affected area, large accumulated rainfall totals, local precipitation exceeding extreme values, and obvious terrain distribution characteristics, with the rainfall process lasting over 72 hours.

On August 2, 2023, China's National Meteorological Center said that the center of the heavy rains would shift to Northeast China. From August 2 to 4, the warm and moist air flow on the periphery of the subtropical high, combined with the influence of cold air, would shift the center of rainfall to areas of Northeast China, with relatively long duration of precipitation. There will be showers or thundershowers in eastern Inner Mongolia and Northeast China, with heavy to torrential rains in some parts of eastern Inner Mongolia, most of Jilin, southern and eastern Heilongjiang, and central eastern Liaoning. Localized areas could see extreme torrential rains.