Why is it that the seasons in Kunming are like spring and the annual temperature difference is so small?

Kunming is a spring city because it is located at 25 01'north latitude,102 41'east longitude and 189 1 m above sea level. It is a famous spring city at home and abroad. Surrounded by mountains, the sun is shining, the leaves are green and the flowers are unbeaten. It has the reputation of "colorful flowers never wither, warm in winter and cool in summer, and four seasons are like spring". The annual average temperature in Kunming is 14.6℃, the monthly average temperature is 7.6℃, and the July average temperature is 19.7℃. The annual average temperature 10 ~ 22℃ has 300 days. The rest of the daily average temperature is also close to 10℃ ~ 22℃. The annual average precipitation is 1007mm, which belongs to the humid area of China. . The reasons why Kunming is a spring city are as follows: 1. It is not cold in winter, thanks to the control of dry and warm air flow in the west and the blocking of cold air in the north by plateau topography. In winter, the mid-latitude westerly winds move south. Due to the blocking effect of the Qinghai-Tibet Plateau, the westerly airflow is divided into two streams, bypassing the north and south sides of the Qinghai-Tibet Plateau respectively. Kunming is located in the southeast, just under the control of westerly jet, belonging to the south branch. Under the guidance of westerly jet, the southern branch of high altitude, dry air in the west mainly prevails near the ground. Under the control of this airflow, sunny, warm and dry weather has become the main feature of winter weather in Kunming. Secondly, the Yunnan-Guizhou Plateau has a high terrain and gently slopes from west to east. The cold air in the north goes south, which is blocked by the topography of Yunnan-Guizhou Plateau, and it is difficult to affect Kunming area (except strong cold air). The cold front meets the dry and warm air flow in the west, forming a quasi-static front in Kunming between Kunming and Guiyang (about 104 east longitude). East longitude 104 In the east of Yunnan-Guizhou Plateau represented by Guiyang, the cold air side of Jiajing front in Kunming is overcast, rainy, cold and humid. That is, "it will clear up in three days"; The west of Yunnan-Guizhou Plateau, represented by Kunming, is east longitude 104, controlled by dry warm air flow, and the blue sky is like washing. The blue sky has little effect on the weakening of solar radiation, which makes the amount of solar radiation reaching the ground relatively more than that of Guiyang near the same latitude, so the monthly average temperature in Kunming in winter is about 6℃ higher than that in Guiyang. It can be seen that the winter in Kunming is not cold and sunny. Second, it is not hot in summer, thanks to the high altitude, and the average altitude of Kunming during the same period of rain and heat is1891m. With the increase of altitude, the temperature will decrease, and the temperature will decrease by 6℃ for every increase of 1000 meters, so the monthly average temperature in Kunming in summer is about 10℃ lower than that in Guilin at the same latitude (25 20' north latitude and altitude 166 meters). More than 80% of the annual precipitation in Kunming is mainly concentrated in the five months from late May to 10, which is called "rainy season". Cloudy skies in rainy season hinder and weaken the intense solar radiation in summer, and at the same time, a lot of rainfall increases the evaporation on the ground and takes away a lot of heat. Therefore, in July and August in midsummer, when the heat in the middle and lower reaches of the Yangtze River is unbearable, Kunming is particularly cool and becomes a good place for human resources to escape the heat. Thanks to the adjustment of Dianchi Lake, Dianchi Lake is known as the "Pearl of the Plateau" and is a famous freshwater lake in China. The first couplet in the world, Daguanlou Changlian, is called Dianchi Lake: "Five hundred Li Dianchi Lake enters the eye ..." Today, Dianchi Lake covers an area of about 300 square kilometers and is the largest lake in the province. Kunming is located in the north (shore) of Dianchi Lake Basin, and the wide Dianchi Lake has played a good role in regulating the temperature and relative humidity in Kunming. We know that the specific heat of water is about five times that of land. After water absorbs the heat radiated by the sun, it can be transmitted to the deep layer, while the land can only store the heat in the surface layer. This makes the land warm and cold rapidly. During the day, the land surface of Kunming is hot, and when the water surface of Dianchi Lake is cold, the wind blows from Dianchi Lake to Kunming to bring cool and humid airflow. At night, the surface of Kunming is cold, the surface of Dianchi Lake is warm, and the wind blows from Kunming to Dianchi Lake, which regulates the temperature and humidity of Kunming in one day. In short, due to the above reasons, Kunming has become one of the top 20 spring cities in the world. Due to the special climatic conditions in Kunming, the people of Kunming have the opportunity to welcome people from all over the world on behalf of Yunnan and China to attend the' 99 Kunming World Expo. It is precisely because of Kunming's unique climate that there are many kinds of flowers here and the flowering period is long, giving people a feeling of unbeaten flowers in four seasons. Kunming deserves to be called the Spring City.