What are the characteristics of subtropical monsoon climate?

The average annual temperature in subtropical monsoon climate zone is between 13℃~ 20℃, while the average winter temperature is above 65438+ 10℃, 0℃ ~ 2℃ north of the Yangtze River, 2℃ ~ 10℃ south of the Yangtze River and 10℃ in Nanling area. Jianghan Plain and Dongting Lake Plain are particularly vulnerable to the cold air in the south in winter because of the weak barrier effect of Huaiyang Mountain. The northern part of these two plains is connected with Nanyang Basin and Nantong Gui Xiang Corridor, which become the channel of cold air in the south in winter, and the 65438+ 10 monthly isotherm is tongue-shaped and protrudes southward. The lowest temperature in the north of the Yangtze River can be below-10℃, and in the south of the Yangtze River it is between -7℃ and-10℃. Whenever strong cold air goes south, the temperature often drops above 10℃. In Shanghai, there was a record that the temperature dropped by 25.2℃ in two days. Therefore, although this area is subtropical, the temperature in winter is lower than that in other areas of the same latitude. Due to the low temperature in winter, the subtropical latitude in China is 4 ~ 5 latitudes south of the theoretical boundary. Compared with the Mediterranean region, it is 10 ~ 1 1 latitude. However, subtropical areas in China, especially central China, are generally hot in summer, with the average temperature in July around 28℃ and some areas exceeding 29℃. The average temperature in April and1October is 16℃ ~ 2 1℃, and the temperature in autumn is generally higher than that in spring. High temperature weather above 35℃ often occurs from May to September. July-August is controlled by subtropical high, with many sunny days, long sunshine hours and the highest frequency of high temperature. The absolute high temperature often exceeds 40℃, and there have even been high temperatures above 465 and 438+0℃ in Zhejiang and Hunan.

There are four distinct seasons in the middle and lower reaches of the Yangtze River, with warm winter and hot summer. Generally, it is 1 ~ 4 months in winter, about 4 months in the north of the Yangtze River and less than 1 month in Nanling. Summer usually ends from the middle and late May to the end of September, and may be postponed to the beginning of June in the south 10. Generally speaking, summer lasts at least 4 months. Generally, there will be two months of spring and autumn in various places, but the spring and autumn in southern China may reach more than three months.

The precipitation in subtropical monsoon climate zone is generally higher than that in North China and Southwest China, and its annual average precipitation is generally around 800 mm ~ 1600 mm, in which the precipitation distribution decreases from southeast to northwest. The annual precipitation in hilly areas of Zhejiang Province is 1200mm ~ 180mm, that in Nanling and Jiangnan hilly areas is 1500mm, and that in the middle and lower reaches of the Yangtze River is 1000mm ~ 1200mm. General precipitation will also be affected by topography. There is more precipitation in mountainous areas than in flat land, and there will be more precipitation on windward slopes than on leeward slopes.

Precipitation will change with the seasons. Generally, the precipitation is the most in summer, the least in winter and more in spring than in autumn. But the winter rainfall also accounts for more than one tenth of the annual rainfall. The middle and lower reaches of the Yangtze River are areas with high proportion of winter rain and abundant spring rain in China. The seasonal distribution characteristics of precipitation are closely related to the geographical location of the middle and lower reaches of the Yangtze River and the atmospheric circulation process. To the west of the middle and lower reaches of the Yangtze River is the Qinghai-Tibet Plateau. In winter, there will be a stable shear line formed by the convergence of the north-south jet brought by the west wind over this area. Coupled with the influence of Nanling mountains, there will be a persistent quasi-static front in South China on the ground, which will make cyclones pass through frequently. So there are many rainy days, and there is little precipitation in most areas from 65438 to February. However, since March, the warm and humid air flow from the south has strengthened, which has increased precipitation. In late March, the spring rain centered on Gannan will gradually extend to the northwest, southwest and northeast. In most areas, the spring rain begins in early April and ends in late May. There are more spring rains in this area, and sometimes there are more spring rains than summer rains in Changsha and Nanchang.