Why are Wuhan, Nanjing and Chongqing called "three furnaces"?

In the middle and lower reaches of the Yangtze River in China, there is a high temperature area in summer, such as Nanjing, Wuhan and Chongqing. The highest temperature in China and Japan exceeds 35℃ for more than 20 days in a year, and both of them have experienced high temperature above 40℃, so people also call these three cities "three stoves".

In Turpan Basin, a hot pole in China, an extreme maximum temperature of 49.6℃ was observed on July 1975. However, it is small in size and population, and it is hot but not stuffy. Therefore, in the hottest summer of the year, it is not Turpan that has the greatest impact on people's lives and work, but the Yangtze River basin with a vast area and a large population. During the high temperature in summer, there are three famous "big stoves": Nanjing, Wuhan and Chongqing.

The three stoves in Nanjing, Wuhan and Chongqing are really hot. The average temperature in July is around 33℃, and the extreme maximum temperature has reached 465,438+0.3 ~ 44℃. The high temperature lasts for a long time, and the average number of hot summer days above 30℃ is over 70 days per year. And the temperature doesn't change much from morning till night, not only during the day, but also at night.

The main reason for the formation of the three furnaces along the Yangtze River is that the high altitude in summer is controlled by the subtropical high pressure area; The second is the influence of topography. Chongqing, Wuhan and Nanjing are all located in the lower Yangtze River basin. The topography of the valley is like the bottom of a pot, surrounded by mountains, and the ground is difficult to dissipate heat, which makes the temperature rise continuously. Third, these places are densely covered with rice fields, with a lot of water vapor and high humidity. People are not easy to evaporate after sweating, and the heat dissipation efficiency of sweating is greatly reduced. High temperature and humidity make people feel sultry.

In fact, these three stoves are not too hot. Judging from the days of high temperature above 35℃, Anqing has 20 days, and Hangzhou has 2 1.9 days along the river, both of which are more than Nanjing. Jiujiang has 25 days and Huangshi has 25.6 days, which is also more than Wuhan. Fuling 36.4 days, Wanxian 36.9 days, also above Chongqing. There are more high-temperature "stoves" outside the Yangtze River. For example, it takes 42.7 days in Guixi, Jiangxi, 42.9 days in Hengyang, Hunan and 4 1.6 days in Kaixian, Sichuan.

So why are Nanjing, Wuhan and Chongqing called the three "stoves"? Perhaps it is because they are well-known big cities and the result of propaganda by many literati in history.