Why did frequent rainfall in northwest China turn Gobi into an oasis this year?

On July 24th, Professor Wang Chenghai from College of Atmospheric Sciences of Lanzhou University pointed out in the meteorological lecture held by College of Atmospheric Sciences of Lanzhou University that abnormal atmospheric circulation is the main reason for abnormal precipitation in northwest China. When studying and analyzing the climate characteristics since the summer of 20 19, the earth system model research and development center of Lanzhou University pointed out that there have been many extreme precipitation events, extreme winds and hail disasters in this area. Heavy rains occurred in some arid and extremely arid areas, leading to waterlogging.

When talking about the frequent occurrence of extreme weather events and the obvious increase of meteorological disasters such as heavy rain, heavy rain and hail, Wang Chenghai pointed out. For example, the rainfall data before Dunhuang shows that its annual rainfall is about 40 mm, but in recent years, heavy rain events have occurred frequently. For example, from July 6 to 7 this year, the daily rainfall reached 19 mm, and in some areas it reached 40 mm; The daily rainfall in Jiuquan City is 84.8 mm, and the hourly rainfall in Heshui County in Longdong reaches 90.8 mm, which breaks through the historical limit of Qingyang City. What's more, in July this summer, snowflakes floated on the leisure grassland in southern Jiangsu, indicating frequent abnormal weather events. In addition, the northwest is an arid area, and the precipitation suddenly increases, which easily leads to waterlogging.

As far as its formation is concerned, Wang Chenghai believes that the abnormal atmospheric circulation is the main reason for the abnormal precipitation in northwest China. Last July, the northern region was under the control of the relatively dry and rainy Xinjiang Ridge, but this year, the whole northern region is in the high-altitude trough and in the channel where the trend of warm and humid precipitation in the northwest is increasing, and the rainfall has also increased.

Wang, director of the Meteorological Observatory of Lanzhou University and an associate professor at the College of Atmospheric Sciences of Lanzhou University, said that the increase of high-altitude troughs or vortices on the Qinghai-Tibet Plateau has led to more frequent cold air activities. When cold air meets warm and humid air, it will form precipitation. As for the increasing trend of precipitation in Hexi area of Gansu this summer, the Center for Research and Development of Earth System Model of Lanzhou University pointed out that one of the bases for the forecast is the low sea ice in the Arctic and the sea ice area in the Little Bering Strait. Why are extreme weather events frequent in recent years? Wang Chenghai believes that in the context of global warming, extreme weather events will become more and more frequent and have an increasing trend. With the improvement of human productivity, there are more and more large-scale engineering facilities. Large-scale human activities are one of the causes of local environmental changes and extreme weather events.

Wang Chenghai said that climate is the common heritage of mankind, and we have the obligation and responsibility to protect it. It is very important to respect the laws of nature and organize human activities scientifically and orderly. Climate engineering to mitigate the impact of climate change is also the research direction of future academic circles. He also proposed preventive measures against climate change and extreme weather. For example, strengthen the monitoring and early warning level of extreme weather and improve the ability of disaster early warning; Protect the ecological environment according to local conditions, promote sustainable development and improve the ecological environment; Support the development of scientific experiments in climate engineering, and form a strong support for monitoring and early warning.