Why is it always summer and autumn when it rains?

Lingnan in China is roughly south of the Guide Ridge Mountains, including Guangdong and Guangxi provinces. However, in a broad sense, the Nanling Mountains extend eastward to the Wuyi Mountains in western Fujian, so Fujian and Taiwan Province provinces can also be included. The climate of these four provinces and regions is the warmest in China. There is almost no winter here, and summer lasts for more than five or six months. As for Hainan Island, it lasted more than eight months. In fact, the winter here is very warm. For example, in Guangzhou and Nanning, the average temperature in June is 65438 0.3℃, in Fuzhou, 65438 0.0℃, and in Taipei, 65438 0.5℃. According to the standard of climatology, if the average temperature is below 10℃ every five days, it can be called winter, so only Fuzhou has five days in a year. Therefore, except for a few days in winter, some places need to wear thin cotton-padded clothes, and generally it is enough to clip a piece of clothes. It's always as hot here during the day, from morning till night. If you go to Guangzhou in summer, you will often feel sweaty! It will be cooler only after a rain at this time. No wonder Su Dongpo, a writer in the Song Dynasty, once said that the climate here is "summer at four o'clock and autumn when it rains". Sometimes the weather doesn't change very frequently in a day, so there is a saying that there are four seasons in a day.

Then, why is it that China's Lingnan is characterized by "it's always summer, and when it rains, it becomes autumn"? This is mainly caused by geographical latitude and topographic conditions. Latitude, as can be seen from the map, the Tropic of Cancer is passing through the central parts of Taiwan Province, Guangdong and Guangxi provinces. If divided by geographical latitude, the south of this line is tropical, and the north of this line belongs to subtropical. If divided by the isotherm of1October 65438+10℃, this isotherm passes through the northwest and southwest of Fuzhou, Shaoguan in Guangdong and Liuzhou and Baise in Guangxi, and the south of the line is an area without winter all the year round. Therefore, in terms of geographical latitude, Lingnan in China lies between the tropics and subtropics, and most of them are areas without winter.

Judging from the topographical conditions, Nanling Mountain ranges from Wuling Mountain in northern Guangxi to Guangdong Province in the west and Wuyi Mountain in the west of Fujian Province in the east. Its height is generally around 1, 000 ~ 1, 500m, which can block the cold air from the north to the south in winter, although sometimes the strong cold wave in the north can reach Lingnan, which reduces the daily average temperature in Guangzhou and Nanning to 1 month. Moreover, the terrain here is high in the north and low in the south (high in the west and low in the east of Fujian), which is conducive to receiving warm and humid airflow from the ocean, making the climate here warmer and wetter, so the terrain conditions are also one of the main reasons for the warm and hot climate here.

Due to the above two factors, Lingnan has become the warmest region in China. In fact, the climate here is not divided into four seasons, but into three seasons: cool season, 165438+ 10 ~ February, the northeast monsoon prevails and the climate is the coolest; In the warm season, from March to June, the warm and humid air flow at sea begins to enter, the temperature rises and there is more precipitation; In midsummer season, from June to 10, typhoons often strike, with the hottest weather and the most precipitation. During this period, the daily variation of temperature is also the largest, and the temperature can rise and fall by 6 ~ 8℃ in one day. Therefore, "a rain turns into autumn" is truly in line with objective reality.

Due to the high temperature and rainy weather all the year round in Lingnan area of China, it provides conditions for the growth of tropical crops.