The weather in Shanxi in June is 5438+ 10.

This year's extreme weather is frequent, and the global weather is in an abnormal state. The extreme climate of "drought in the south and waterlogging in the north" in China is very obvious, which makes many people very curious. What's going on here? Is the map upside down?

0 1, with frequent rainstorms in the north.

In the past few years, the northern region has been dry and rainy. The annual precipitation time is mostly from June to September, and it seldom rains after autumn. But this year is different. From June 5438+ 10, a wave of heavy rainfall caused 76 counties in Shanxi 1757 10000 people to be affected, 12000 people were moved urgently, and 2,849,600 mu of farmland was affected.

In previous years, the cumulative average precipitation in June 5438+ 10 in Shanxi was 3 1. 1mm, but this year, precipitation monitoring stations in many places in Shanxi broke the historical extreme, such as Daning County and yingze district, where the precipitation exceeded 250mm, and Wenshui County (district, city) and other counties (districts, cities) had/kloc-0. ..

In addition to Shanxi, the precipitation in Shaanxi has also increased significantly since 5,438+10 in June, with the precipitation being 60% higher, and it suffered the strongest rainfall in the past 60 years. Since the flood season, the cumulative precipitation in Shaanxi has been 823. 1 mm, but due to the continuous rainfall, the farmland water in many places in Shaanxi is almost saturated, and geological disasters are prone to occur.

The rainstorm in Shaanxi and Shanxi has a long rainfall time and obvious rainfall. In fact, Xi 'an has had precipitation for more than half a month since September. In addition, in July, Henan also suffered a heavy rainfall, which caused serious economic losses.

In everyone's impression, the rainfall in the north is usually less, but we are often worried about drought and lack of rain, but this year the rainfall in the north has exceeded that in the south.

02. Staged drought in southern China

There is obviously little rain in the south this year. In the summer and autumn when it should be raining heavily, the rainfall this year is less, and even water supply has become a problem in many places. Take Guangdong as an example. Since last autumn, there has been an obvious drought in eastern Guangdong, and it has not rained for a long time. Baipenzhu Reservoir has been below the stagnant water level for four months, and the water supply in some towns is limited, so the problem of crop drought is serious.

In Jiangxi, from the beginning of July, the range of moderate drought accounted for 54.8% of the whole province, and parts of northern Jiangxi, southern Jiangxi and central Jiangxi were in severe drought. The same is true in Hunan. Since September, precipitation has been greatly reduced, and the climate in nearly 50% areas is dry.

03. Why is there a phenomenon of "drought in the south and waterlogging in the north"?

In September this year, the rainfall in northern China was more than twice that in previous years, and the rainfall in Beijing-Tianjin-Hebei, Lu Yu-Shanxi, Liaoning and other places exceeded the historical peak 196 1. Why does this problem occur in this year's rainfall?

1, atmospheric circulation anomaly

Ren Guoyu, a meteorologist, said that the heavy rainfall in the north this year was actually related to the abnormal atmospheric circulation in the northern hemisphere and East Asia, which continued in the Year of the Rat. The fluctuation of high-altitude circulation in middle and high dimensions is relatively strong, and the exchange and fluctuation of cold and warm air between north and south are frequent, which has a great influence on China.

At the same time, the intensity of subtropical high is relatively large and strong in the north, covering most parts of South China, making the high temperature in the south more obvious. Due to the strong subtropical high, the air flow can only fluctuate at the edge of the subtropical high, and there is enough warm and humid air flow in the ocean, which collides with the strong cold air in the south.

The collision zone is just at the northwest edge of the subtropical high, and a rain belt is formed under the collision, that is, the Sichuan Basin to North China and Northeast China, which lasts for a long time and has a large amount of rainfall. In South China, due to the typhoon moving on the edge of subtropical high and landing in Hainan this year, it is difficult for warm and humid air to invade the hinterland of the south, so there is little rainfall and the south is dry and hot.

2. Cold air goes south in advance

Due to the influence of global warming, the melting of Arctic glaciers has accelerated, and a large amount of cold air has been released. As a result, the cold air moved south in advance. On the other hand, the subtropical high should have left China in September, but this year, instead of leaving, it moved to the Yellow River basin and remained there until June 10.

As a result, the cold air heading south in advance collided with the subtropical high-heat air, and a series of chemical reactions occurred, thus causing heavy rain. Of course, the probability of La Nina phenomenon this year is 80%, and the characteristic of La Nina in China has always been "drought in the south and waterlogging in the north". In La Nina year, high-pressure air mass is prone to appear on the east side of the equator, which induces subtropical high to continue northward, resulting in more precipitation in North China.

Because of this, heavy rains that occur once in decades frequently in the north this year. Some people may say that the north has been short of water, and more precipitation is not a bad thing. In fact, this year's precipitation did not land at the most appropriate time. On the contrary, crops in the north had a bumper harvest in September. At this time, precipitation can only be forced to postpone the harvest of corn and soybeans, and the sowing of winter wheat is also affected, which is not good for the agricultural industry.

Experts predict that in the next few years, the global extreme weather will only increase, and most of them are sudden extreme weather. It is difficult to prevent it in advance with the existing forecasting methods. Next, the government should take emergency measures, such as building small and medium-sized reservoirs to give full play to their water storage capacity, and at the same time increase publicity on disaster prevention and mitigation on weekdays. what do you think?