What is the impact of increased precipitation?
Core reading
This summer, the number of rainy days in the Beijing-Tianjin-Hebei region has increased significantly.
According to statistics, from June 1 to August 31, the average precipitation in the three provinces of Beijing-Tianjin-Hebei reached 508 millimeters, which was nearly half of that in the same period of normal years.
Why has the precipitation increased in the Beijing-Tianjin-Hebei region?
What impact did it bring?
How to seek advantages and avoid disadvantages?
On September 8, Beijing once again ushered in rainy weather.
"This summer has a lot of rain" "It seems to rain twice in three days"... In the Beijing-Tianjin-Hebei region, many people have a common feeling: "It will rain a lot this year!"
The monitoring data of the Meteorological Department confirms everyone’s feelings: This summer (June 1 to August 31), the average precipitation in the three provinces of Beijing, Tianjin and Hebei reached 508 mm, which was nearly half of the normal period in 1997. The most since the same period.
The rainy season in North China is 6 days earlier than normal, and it has not yet ended, and the end date is obviously late
Gu Wei, a senior engineer at the Climate Prediction Office of the National Climate Center of China Meteorological Administration, said: "This summer, the spatial distribution of precipitation in North China is quite different, and most of the areas are mainly located in the Beijing-Tianjin-Hebei region in the middle-eastern part of North China."
The monitoring data released by the Beijing Municipal Meteorological Department shows that from June 1 to August 31, the city’s average precipitation was 627.4 mm, which is nearly 70% and 60% higher than the same period in normal years and the same period in the past 10 years, which is the past 20 years. most.
Gu Wei said: "The rainy season in North China began on July 12, 6 days earlier than normal. Moreover, the rainy season in North China has not yet ended, which is significantly later than the end of the normal rainy season (August 18). As of September 7, Beijing and Tianjin The average rainfall in the rainy season in the three provinces of Hebei is 398 millimeters, 65.5% more than normal." The forecast issued by the Central Meteorological Observatory at 18:00 on September 8 shows that in the next three days, affected by the cold vortex, there will be more showers or thundershowers in the central and northern parts of North China. It is accompanied by strong convective weather such as short-term heavy rainfall, thunderstorms and gales.
"In the three months of summer from June to August, the precipitation in July in Beijing-Tianjin-Hebei was significantly higher than that in the same period of normal year. The abnormal precipitation in July played a leading role in the heavy rainfall this summer." Gu Wei introduced, July The subtropical high in the western Pacific is relatively strong, and its location is west and north. North China is at the western edge of the subtropical high, with unstable convection and sufficient energy.
At the same time, convection in the South China Sea and the Northwest Pacific was active in July. Typhoon No. 6 "Fireworks" developed in the Northwest Pacific and Typhoon No. 7 "Chapaca" developed simultaneously in the South China Sea, which strengthened the transportation of water vapor from the Northwest Pacific, the South China Sea and the Bay of Bengal. It provides an abundant source of water vapor for heavy rainfall in North China such as Beijing-Tianjin-Hebei.
Since September, the Beijing-Tianjin-Hebei region has experienced a significant precipitation process, with an average precipitation of 39.8 mm, of which the Beijing area reached 64 mm, which has exceeded the average annual rainfall of Beijing in September (54 mm).
Gu Wei said: "It is expected that there will be significant precipitation in the Beijing-Tianjin-Hebei region in mid-to-late September, and the amount of precipitation will be 20% to 50% more than that of the same period of normal years."
Increased precipitation provides favorable conditions for carrying out ecological regulation of rivers and lakes and restoring groundwater levels
"Since the beginning of summer, the Beijing-Tianjin-Hebei region has had more precipitation than normal over the same period of the year. The spring drought has obviously been relieved, which is conducive to reservoir water storage, agricultural production, and air quality improvement." Yin Yizhou, deputy director of the Disaster Risk Office of the National Climate Center of China Meteorological Administration, introduced. From June to August, the average runoff depth of the Haihe River Basin was 35.3 mm, which was more than half of that of the same period of normal years. The accumulated precipitation in the upstream basins of Beijing Miyun Reservoir, Hebei Panjiakou Reservoir and Yuecheng Reservoir was 67.8% and 66.8% higher than normal. , 41.9%.
The increase in precipitation has increased the water storage capacity of rivers and lakes and reservoirs, providing favorable conditions for the development of ecological regulation of rivers and lakes and the restoration of groundwater levels.
In July, this summer, the ecological water replenishment of Hutuo River and Daqing River (Baiyangdian) was successfully completed, and the water replenishment volume reached 221 million cubic meters.
Compared with before water replenishment, the groundwater level within 2 kilometers of the water replenishment channel rose by an average of 0.33 meters; the number of fish species in the Zhaowangxin River, Ziyaxin River, and Ziya River increased by 25%, 33%, and 20% respectively during the water replenishment period. .
Starting from the end of August, the Haihe Water Resources Commission of the Ministry of Water Resources will coordinate the Guanting Reservoir inflow, water diversion from the Yellow River, water from the middle route of the South-to-North Water Diversion, North Canal water and other water sources, which will run through the 146 km section of Yongding River from Beijing Sanjiadian to Tianjin Qujiadian. The total amount of ecological water supply is about 140 million cubic meters.
"More precipitation is conducive to improving air quality." Yin Yizhou said.
Taking Beijing-Tianjin-Hebei as an example, the monitoring data released by the Ministry of Ecology and Environment showed that the percentage of days with good air quality in Beijing-Tianjin-Hebei and surrounding areas "2+26" cities was 71.1%, a year-on-year increase of 14 percentage points. ; PM2.5 concentration was 21 micrograms/m3, a year-on-year decrease of 43.2%.
The proportion of days with good air quality in Beijing in July was 83.9%, a year-on-year increase of 29.1 percentage points; the PM2.5 concentration was 16 micrograms/m3, a year-on-year decrease of 50%.
"The average precipitation in the Beijing-Tianjin-Hebei region this summer is 166.7 millimeters more than that in the same period of normal year, which is equivalent to 36.3 billion tons of rain fell more than the same period of normal year." Gu Wei said, "However, the current precipitation in the Beijing-Tianjin-Hebei region is relatively local In terms of climatic averages, it does not mean that there is no shortage of water. In terms of precipitation values, there are still significant differences between the Beijing-Tianjin-Hebei region and the southern region."
Improve the construction of flood control engineering system and improve forecasting and early warning capabilities
"This summer, the Beijing-Tianjin-Hebei region has more precipitation overall, but the spatial distribution is uneven. Among them, the precipitation in eastern Beijing, most of Tianjin, northeastern Hebei, and southern Hebei is more than 50% more." Yin Yizhou said.
This summer, precipitation extremes in some weather stations in Beijing, Tianjin and eastern Hebei were obvious. A total of 8 national-level ground weather stations in the Beijing-Tianjin-Hebei region exceeded the monthly extreme value of the same period in history, and Beijing Shunyi exceeded the annual extreme value.
"Judging from the precipitation in Beijing, Tianjin, Hebei and other places this summer, it is necessary to further strengthen the monitoring and forecasting capabilities in disaster prevention and mitigation in the future, and improve the early warning service capabilities for extreme weather and climate events, so as to achieve precise monitoring, accurate forecasting, and fine service." Yin Yizhou said that at the same time, it is necessary to further improve the mechanisms and procedures of each link of flood prevention and disaster relief, increase inspections of dangerous sections of dikes, dangerous reservoirs, and urban drainage and waterlogging prevention facilities, and do a good job in the investigation and repair of hidden dangers.
Increased rainfall has brought challenges to flood control in the Haihe River Basin.
According to the person in charge of the Information Center of the Ministry of Water Resources, the Haihe River system is distributed in a fan shape, the rivers flow into the sea, and the "linear series" effect of flood propagation is relatively poor.
In addition, the mountains and plains in the basin have a short transition. From rainfall in the mountains to flooding at the river mouth, the longest foreseen period is only 1 to 2 days, and the shortest is only a few hours.
Therefore, floods generally rise and fall steeply, with concentrated flood volume and high peaks, making defense difficult.
At present, the Haihe River Basin has initially established a flood control engineering system with reservoirs, river dikes, and flood storage and detention areas as the main body.
There are 1,597 large, medium and small reservoirs with flood control functions in the whole basin, with a total storage capacity of 31.55 billion cubic meters; the whole basin has a total of 21,630 kilometers of dikes above level 5.
The water conservancy department is further improving the construction of the flood control engineering system, improving the forecasting and early warning capabilities, and improving the accuracy of the joint scheduling of water engineering.
"In addition, it is necessary to increase scientific publicity, so that all sectors of society are fully aware of the increased risk of extreme weather and climate events in my country under the background of global warming, and improve the general public's awareness of disaster prevention and mitigation and the ability to prevent floods and floods." Yin Yizhou said.
Layout design: Zhang Danfeng
Our reporter Liu Yi and Wang Hao