Why is it that the altitude in central and southern Yunnan 1000 ~ 1500m is like spring all the year round?

The altitude in south-central Yunnan is 1 1,000 ~11,500 m. In summer, because the altitude is higher than the ground pressure near the same latitude, the temperature begins to drop below 22℃. In winter, due to the blocking of cold air from north to south by the Qinghai-Tibet Plateau and the Dongpo Mountain of Yunnan Plateau, cold waves rarely invade. In addition, the latitude is low, the sun is full of light and heat, and the average temperature can still be kept above 10℃. On the eastern mountain with the same latitude and height, although summer is as cool as spring and autumn, winter is often in the cold air sea south of Siberia, which leads to the temperature in winter being much lower than 10℃, so there is no spring-like climate all year round. It can be seen that it is precisely because of the comprehensive effect of topography and altitude that the areas in central and southern Yunnan with an altitude of 1 1,000 ~11,500 meters can enjoy the climate like spring all the year round. In Yunnan, where the seasons are like spring, the climate characteristics are quite different due to the different topography. On the topography of the basin (called bazi in Yunnan), the temperature rises rapidly after the sun comes out because of poor airflow, and the temperature in the basin is higher than that on the flat land at the same height outside the basin during the day. When the ground radiation cools down at night, the low-temperature airflow (mountain wind) flowing from the surrounding high slope to the bottom of the basin makes the temperature in the basin lower than the same level outside the basin. That is to say, the topography of the basin increases the daily variation of temperature in the basin. Take Kunming for example (there is still a warm winter in Kunming, so the four seasons are like spring, but it does not prevent us from taking this as an example to illustrate the problem): In June, the average maximum temperature in Kunming rose to 15.8℃ in the afternoon, and it was even higher in sunny days, so people often felt sleepy at noon in spring; However, the average minimum temperature in the morning is only 65438 0.7℃, and sub-zero temperature often appears at night, with clear breeze or occasional cold air. In April, the highest temperature in Kunming in the afternoon averaged 24.8℃, which was quite summer in the sun. But the lowest temperature in the morning is only 10. 1℃. It can be seen that the four seasons in the basin are as solid as spring, but "there is winter and summer every day". Of course, because the low temperature period happens at night, people often rest indoors, and there is actually no obvious feeling of winter and summer. Therefore, only on the ridge at the top of the mountain, due to the frequent blowing and adjustment of the high-altitude airflow with little daily temperature change, the seasons are like spring, which belongs to the real constant spring world.