What are the characteristics of winter and summer temperatures in the mountainous areas of western Sichuan Plateau and Sichuan Basin?

The western Sichuan Plateau is a part of the southeastern margin of the Qinghai-Tibet Plateau and the Hengduan Mountains. The ground is 4000-4500 meters above sea level, which is divided into two parts: western Sichuan Plateau and western Sichuan Mountain. The dividing line between the western Sichuan Plateau and the Chengdu Plain is Qionglai Mountain in Ya 'an today, and the western Sichuan Plateau is in the west of the mountain. The topography of northwest Sichuan Plateau inclines from west to east and is divided into hilly plateau and plateau. Hills and valleys alternate, the valleys are wide and round, sparsely arranged, and swamps are widely distributed. Shanxi in western Sichuan is high in the north and low in the southeast. According to the cutting depth, it can be divided into alpine plains and alpine canyons. The western Sichuan Plateau, where mountains and rivers compete for hegemony, rivers run, and the source and main tributaries of the Yangtze River have nurtured an ancient and mysterious civilization.

The western Sichuan Plateau is located on the east side of the Qinghai-Tibet Plateau. Winter is mainly affected by cold and high pressure, with sunny weather and abundant sunshine. If there is a strong warm and humid air flow, precipitation (snowfall) can be formed. Otherwise, it is mainly sunny. The three-dimensional climate formed by the special geographical location largely makes up for the defects caused by the unclear four seasons in time. Through comprehensive analysis, three climatic zones of economic development are obtained: subtropical zone, temperate zone and cold zone, which have application value for comprehensive utilization of three-dimensional climatic resources and adjustment of industrial structure.

The annual temperature in this area is high, the dry and wet seasons are distinct, and there is little precipitation. There are seven months of dry season throughout the year. Typical dry-hot valley climate is formed in the valley area affected by foehn, and obvious three-dimensional climate is formed in the mountain area. There are few clouds, many sunny days and long sunshine hours in this area. The sunshine hours in the whole year are mostly 2000-2600 hours, which is more than that in the river basin 1000- 1600 hours.

………………………………………………………………………………………………………………

Sichuan Basin is one of the four great basin in China. It is surrounded by connected mountains, located in the south-central part of the Asian continent, in the heart of China and in the middle of the eastern edge of China. The total area is about 260,000 square kilometers, which can be clearly divided into two parts: marginal mountain and basin bottom, with an area of about 654.38+10,000 square kilometers and160,000 square kilometers respectively. Generally, there are 2 ~ 5 vertical natural zones from bottom to top in marginal mountainous areas.

The elevation of mountainous areas in Sichuan Basin is mostly between 1000 meters and 3000 meters. The basin bottom is low, with an altitude of 200-750 meters. Red rock series are widely exposed on the surface, which is called red basin. The western part of the basin is low-lying and fertile, and Dujiangyan water conservancy project has been built in Chengdu, northwest China. The eastern part of the basin is low mountains and hills. Fangshan Hill in the middle of the basin, accounting for 62% of the total area, is mainly composed of purple sandstone and shale. The basin also contains coal, oil, natural gas and minerals, such as salt, apatite and sulfur.

The terrain of Sichuan basin is closed, and the temperature is higher than other areas at the same latitude. The average temperature in Leng Yue is 5 ~ 8℃, which is 2 ~ 4℃ higher than that in Shanghai, Hubei and Guizhou at the same latitude. Extreme minimum temperature -6 ~-2℃. Frost and snow are scarce, and the frost-free period is 280 ~ 350 days throughout the year. In winter, there is constant frost and snow in Wuhan at the same latitude, and Changning, whose basin is located in the Yangtze River basin, is frost-free all the year round. Summer in all parts of the river basin begins at the end of May and lasts for more than 4 to 5 months. The temperature is high in the east and low in the west. The summer temperature in the west is 3-4 degrees lower than that in Shanghai, Wuhan and other cities at the same latitude, but the humidity is unbearable. The average temperature is around 25℃, with high temperature in the southeast and low basin edge. The temperature is as high as 26 ~ 29℃ in the hottest month, and nearly 30℃ in the Yangtze River basin. The sunny, hot and high temperature weather in midsummer caused a severe summer drought in the southeast of the basin. The annual average temperature is 16 ~ 18℃. The active accumulated temperature above 10℃ is 4500 ~ 6000℃ and lasts for 8 ~ 9 months, belonging to the middle subtropical zone. The accumulated temperature in the southeast Yangtze River basin exceeds 6000℃, which is equivalent to the tropical climate of South Asia south of Nanling in China. The temperature in the basin is high in the east and low in the west, high in the south and low in the north, high in the bottom and low in the edge, and the isotherm distribution is concentric.

The temperature in the mountainous area on the edge of the basin has vertical distribution characteristics. The elevation of Emei Mountain and Jinfo Mountain rises by 100 m, and the temperature drops by 0.55℃ and 0.6 1℃ respectively. The average annual temperature at the top of Mount Emei is only 3℃, and the active accumulated temperature above 10℃ is 586℃, which is equivalent to cold temperate zone and sub-cold zone in climate.