Jiangsu was hit by a tornado. Big data reveals when and where tornadoes are prone to occur in China.

　　China Weather Network News Affected by surface cyclones, severe convective weather occurred in many places in Jiangsu yesterday (July 20th), among which Suqian Shuyang and Lianyungang Guannan were even hit by tornadoes. As a small-scale weather system, tornado has a short life, but it is extremely destructive. It comes as soon as it comes, and people can’t avoid it. Is there a rule for tornadoes to follow? China Weather Network analyzes meteorological big data to reveal when tornadoes are most frequent in China and which areas are more prone to them.

　　Tornadoes are extremely destructive and can blow cars and destroy houses.

　　Tornado, as a kind of strong destructive convective weather, is a small-scale air vortex produced under strong unstable weather conditions. The central wind force can reach 50-150 m/s, and the diameter is generally between several meters and hundreds of meters.

　　Tornadoes are generated and disappeared rapidly, often accompanied by strong convective weather systems such as thunderstorms, hail and heavy rain, which are extremely destructive. According to Fujita scale, the tornado strength is divided into six grades: EF0 to EF5, with EF0 being the lowest and EF5 being the highest.

　　Tornadoes of EF2 and above are generally called strong tornadoes, and EF2 tornadoes will cause considerable damage, which may lead to the uprooting of trees; EF3 tornadoes often cause serious damage, and trains may be blown down. EF4 tornado may cause destructive damage, good brick-wood structure and frame structure houses may be destroyed, and some houses will be shoveled and leveled by Qi Gen; The damage caused by EF5 tornado is devastating. The house with frame structure may be thrown out together with the foundation, the reinforced concrete structure building will be seriously damaged, and the car may be blown away.

　　Tornadoes have occurred in most parts of China, with the largest number in Jiangsu and Guangdong.

　　Global tornadoes mainly occur in mid-latitude areas, and tornadoes occur every year in North America, Europe, Russian Federation, China, Japanese and Australian, among which the United States is the country with the most tornadoes, with an average of 1,141 tornadoes recorded every year (from 2000 to 2020), which is called "Tornado Kingdom".

　　Tornadoes in China mainly occur in the eastern plain, and the middle and lower reaches of the Yangtze River are frequent areas. According to the statistical data of the National Climate Center from 1991 to 2020, there are 38 tornadoes every year in China, and there are more tornadoes in Jiangsu, Guangdong, Hubei and Anhui provinces, among which Jiangsu and Guangdong have the most tornadoes, with an average annual number of 4.8 and 4.3 respectively, followed by Hubei and Anhui, with two tornadoes.

　　Strong tornadoes occur frequently in spring and summer in China, and most frequently in July.

　　Spring and summer are tornado-prone seasons in China, and the number of tornadoes accounts for 92% of the whole year from April to August, with July accounting for the highest proportion, accounting for about 30%. Judging from the occurrence time of tornado of EF2 and above, it is also the most in July.

　　According to the statistical data of "Temporal and Spatial Distribution of loong Tornadoes", there were 165 tornadoes of EF2 and above in China from 1961 to 2010, and the occurrence time was mainly from April to August. Looking at a single month, July was the most, accounting for 28% of the total number of the year, followed by April.

　　In addition, the months of tornadoes in different regions are slightly different. South China frequently occurs from April to May, the middle and lower reaches of the Yangtze River frequently occur in April and July, North China frequently occurs from June to July, Northeast China frequently occurs from June to August, Southwest China mainly occurs from July to August, and Northwest China frequently experiences tornadoes in July.

　　Tornadoes prefer the afternoon and the evening.

　　In addition to seasonal differences, the time of the tornado’s haunting in one day also has certain rules, and the tornado prefers to "haunt" in the afternoon.

　　According to the statistical data of "Temporal and Spatial Distribution of loong Tornado", from 1961 to 2010, tornadoes occurred from 12: 00 to 20: 00, accounting for 70% of the total number of tornadoes whose time records can be found. The reason for the high incidence in this period is that the atmospheric stratification is unstable after daytime solar radiation, and strong convective weather is most likely to occur, which is easy to promote the formation and strengthening of tornado weather system.

　　In addition to the high-incidence period in the afternoon, the tornado often appears in the early hours of the morning. According to statistics, there are also 10 tornadoes generated from 0: 00 to 2: 00. Tornado occurred less in the morning, with the least occurrence from 10: 00 to 12: 00, only once.

　　There are 38 tornadoes in China every year, with a maximum of 75 in 2005.

　　Judging from the interannual changes, the periodicity of tornadoes is also obvious. According to the statistics of tornado data recorded from 1991 to 2020, there are an average of 38 tornadoes every year in China. There were relatively many tornadoes from the mid-1990s to the beginning of this century. There were relatively few tornadoes in the early 1990s and from 2006 to 2020. Among them, the number of tornadoes was the highest in 2005, reaching 75, and the least in 2020, only 13.

　　What should I do if I encounter a tornado?

　　Tornado is a kind of severe convective weather. After the tornado is formed, it usually lasts for ten minutes to several hours. Its attack range is small, but its destructive power is great. Once encountered, how should we defend ourselves?

　　First, if you are at home, be sure to stay away from doors, windows and the outer walls of houses, and hide in the wall or small room opposite to the tornado. The basement or semi-basement is the safest place to avoid the tornado;

　　Second, in the emergency of pole falling and house collapsing, the power supply should be cut off in time to prevent electric shock or fire;

　　Third, when there is a tornado outside the field, you should look for low-lying ground nearby, but stay away from trees, telephone poles, billboards, fences, etc. to avoid being smashed, crushed or electrocuted;

　　Fourth, when you encounter a tornado when you go out by car, you should drive in the opposite direction, or leave the car immediately and take shelter in a low-lying area.

　　Reference article:

　　[1] soldier said climate "tornado activity and climate characteristics in China and the United States"

　　[2] Fan Wenjie, Yu Xiaoding. 2015. Temporal and Spatial Distribution Characteristics of loong Volume. Meteorology, 41 (7): 793-805.

　　[3] National Climate Center "Why are severe convective weather frequent recently? The authoritative climate cause analysis is coming! 》

　　[4] Dapeng Huang, Zhao Shanshan, Gao Ge, et al. Study on the Characteristics of Tornado Disaster in China in Recent 30 Years [J]. Rainstorm Disaster, 2016,35 (2): 97-101.