Torrential rains in Henan and Shanxi, and the "drought in the south and floods in the north" climate are really abnormal. What happened?

This year’s extreme weather can be said to have broken out frequently. The global weather is in an abnormal state, and the extreme climate of "drought in the south and flood in the north" in China is very obvious, which makes many people very curious. What is going on? Already? Did you hold the map upside down?

01. Frequent heavy rains in the north

In the past many years, the northern region has been dry and dry. Most of the rainfall occurs from June to September every year, and there is very little rain after autumn. But this year is different. Starting in October, a wave of heavy rainfall affected 1.7571 million people in 76 counties in Shanxi. 120,000 people were evacuated urgently and 2.8496 million acres of farmland were affected.

In previous years, the cumulative average precipitation in October in Shanxi was 31.1mm. However, this year, precipitation monitoring stations in many places in Shanxi exceeded historical extreme values. For example, precipitation in Daning County, Yingze District, Wenshui, Fenxi, etc. exceeded 250mm. Precipitation in counties (districts and cities) is between 100-250mm, setting a record.

In addition to Shanxi, precipitation in Shaanxi has also increased significantly since October, with 60% more precipitation and the strongest rainfall in the past 60 years. Since the beginning of the flood season, the cumulative precipitation in Shaanxi has been 823.1mm. Due to continuous rainfall, farmland water in many places in Shaanxi is nearly saturated, making geological disasters more likely.

The heavy rains in Shaanxi and Shanxi lasted for a long time and the rainfall was obviously heavy. In fact, Xi'an has been experiencing precipitation for more than half a month since September. Going further, Henan also suffered heavy rainfall in July, causing heavy economic losses.

In everyone’s impression, the north usually has less rainfall and often suffers from drought and lack of rain. However, this year the north has more rain than the south.

02. Periodic drought in the South

There is obviously less rain in the South this year. In the summer and autumn when there should be heavy rains, there is less rain this year. In many places, water supply has even become a problem. Take Guangdong as an example. Eastern Guangdong has been noticeably dry since last autumn, with no rainfall for a long time. The Baipenzhu Reservoir has been under the dead water level for four months. Some towns have limited water supply, and crops have been seriously affected by drought. .

In Jiangxi, starting from early July, the moderate drought range accounted for 54.8% of the province, and some areas in northern Jiangxi, southern Jiangxi, and central Jiangxi were in severe drought. The same is true for Hunan. Starting from September, precipitation has decreased significantly, and nearly 50% of the area has experienced drought conditions.

03. Why does the phenomenon of “drought in the south and flood in the north” occur?

In September this year, the rainfall in the northern region was more than twice that of previous years, with precipitation in Beijing-Tianjin-Hebei, Shandong, Henan, Shanxi, and Liaoning exceeding record highs since records began in 1961. Why is this problem happening with rainfall this year?

1. Abnormal atmospheric circulation

Meteorological expert Ren Guoyu analyzed that the reason why there is more rain in the north this year is actually related to abnormal atmospheric circulation in the northern hemisphere and East Asia, and this phenomenon has already As the Year of the Rat continues, the high-altitude circulation in medium and high dimensions is relatively volatile, and the exchange and fluctuation of cold and warm air from the north to the south is more frequent, and my country is greatly affected by this.

At the same time, because the subtropical high pressure is relatively strong and stronger to the north, covering most of South China, the high temperature in the south is more obvious. Due to the strong subtropical high, the airflow can only fluctuate at the edge of the subtropical high. In addition, there is sufficient warm and moist airflow from the ocean to collide with the strong cold air moving south.

The collision area is just at the northwest edge of the subtropical high. A rain belt was formed under the impact, that is, from the Sichuan Basin to North China and Northeast China. It lasted for a long time and had heavy rainfall. . In South China and Jiangnan, because typhoons move on the edge of the subtropical high and mostly land in Hainan this year, it is difficult for warm and humid air to invade the hinterland of the south, so there is little rainfall. The south is drier and hotter.

2. Cold air moves south ahead of schedule

Due to the influence of global warming, Arctic glaciers melt faster and release a large amount of cold air. As a result, the cold air moves south ahead of schedule. On the other hand, the Deputy High Commissioner was originally supposed to leave China in September, but not only did he not leave this year, he moved towards the Yellow River Basin and still refused to leave in October.

As a result, the cold air moving south in advance and the hot air from the subtropical high collided with each other, and a series of chemical reactions occurred, resulting in heavy rain. Of course, the probability of La Niña occurring this year is 80%, and the characteristics of La Niña in China have always been "drought in the south and floods in the north." In years with La Niña, high-pressure air masses tend to appear east of the equator, which induces the subtropical high to continue to move northward. As a result, North China experiences excessive rainfall.

Because of this, this year there have been frequent heavy rainfall events in the north that have only occurred once in decades. Some people may say that the north has always been short of water, so more precipitation is not a bad thing. In fact, this year's precipitation did not fall at the most appropriate time. Instead, northern crops ushered in a bumper harvest in September. At this time, the precipitation could only delay the harvest of corn, soybeans, etc., and also affected the sowing of winter wheat, which had a negative impact on agriculture. Industry is unfavorable.

Experts predict that in the next few years, there will only be more and more extreme weather around the world, and most of them will be sudden extreme weather. With the existing prediction methods, it is difficult to prevent in advance.

Next, the government will also take emergency measures, such as building small and medium-sized reservoirs to maximize their water storage capacity. At the same time, it will also increase publicity on disaster prevention and reduction on weekdays. What do you think?