Sincere question! What are the climate characteristics and temperature conditions in the Sichuan Basin in summer?
Chengdu is located in the middle reaches of the Minjiang River in the west of the Sichuan Basin, with an altitude of 387-5364 meters. It is bounded by the Longquan Mountains to the east and Qionglai Mountain to the west. To the west is the Longmen Mountains running from north to south. The plain area accounts for 36.4%, the hilly area accounts for 30.4%, and the mountainous area accounts for 33.2%. The plain area is higher in the northwest and lower in the southeast, with an average slope drop of 0.3%. It has a subtropical humid monsoon climate with four distinct seasons. There is no severe heat in summer and no severe cold in winter. The annual average temperature is 16.7℃. The annual mean daily temperature in the Sichuan Basin is higher than other areas at the same latitude due to its occluded topography. The average temperature of the coldest month is 5 to 8°C, which is 2 to 4°C higher than that of Shanghai and Wuhan at the same latitude and Guiyang in the south. The extreme minimum temperature is -6~-2℃. Frost and snow are rare, and the annual frost-free period lasts 280 to 350 days. Changning, located in the Yangtze River Valley, is frost-free throughout the year.
Summer begins in late May in various parts of the Sichuan Basin and lasts for more than 4 to 5 months. The temperature in the hottest month is as high as 25 to 29°C, and nearly 30°C in the Yangtze River Valley. The extreme highest temperature in the southeastern part of the basin often exceeds 40°C. ℃, Chongqing and Pengshui once experienced 44℃, so Chongqing is also one of the three "furnaces" in the Yangtze River Basin. Continuous sunny and high temperatures in midsummer caused severe summer drought in the southeastern part of the basin.
The average annual temperature in various places is 16~18℃. The active accumulated temperature above 10℃ is 4500-6000℃ and lasts for 8-9 months. It belongs to the mid-subtropical zone. The temperature in the Yangtze River Valley in the southeast exceeds 6000°C, and the Qijiang River exceeds 6100°C, which is equivalent to the southern subtropical climate south of China's Nanling Mountains. The temperature in the basin is high in the east and low in the west, high in the south and low in the north. The basin bottom is high and the edge is low. The isotherm distribution is concentric. The temperature in the mountains on the edge of the basin has vertical distribution characteristics. For example, as the altitude of Mount Emei and Jinfo Mountain increases by 100 meters, the temperature decreases by 0.55°C and 0.61°C. The annual average temperature on the top of Mount Emei is only 3°C, and the accumulated temperature for activities above 10°C is 586°C. The climate is equivalent to the cold temperate zone and subarctic zone.
The annual precipitation in the Sichuan Basin is 1,000-1,300 mm, and the mountains on the edge of the basin have very abundant precipitation. For example, the annual precipitation in the mountains on the western edge between Leshan and Ya'an is 1,500-1,800 mm, making it a prominent rainy area in China. , known as the "West China Rain Screen". However, winter drought, spring drought, summer floods, and autumn rains are unevenly distributed throughout the year, with 70 to 75% of the rainfall concentrated between June and October. The maximum daily precipitation can reach 300 to 500 mm. "Bashan Night Rain" has been famous since ancient times, and night rain accounts for more than 60-70% of the total rainfall. The basin area is foggy and wet, with low clouds and many cloudy days. Mount Emei and Mount Jinfo are the areas with the most foggy days in China, and their annual relative humidity is the highest in China. The annual sunshine in the basin is only 900 to 1,300 hours, and the annual solar radiation is 370 to 420 kilojoules/square centimeter, both of which are the lowest values in China, so it is said to be "Sichuan dog barking at the sun". The number of sunshine hours is 1071 hours, and the average annual rainfall is 945.6 mm. The urban area of Chengdu is located in the eastern part of the Chengdu Plain, with an average altitude of about 500 meters. The Chengdu Plain is the largest plain in southwest my country. The Dujiangyan Irrigation Project, located on the main stream of the Minjiang River, has a network of irrigation canals spread out in a fan shape on the vast Chengdu Plain, making the Chengdu Plain a "land of abundance" where "people are affected by floods and droughts, but not by famine".
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