As mentioned above, the quasi-static front in Kunming is the interface between the polar metamorphic continental air mass and the tropical continental air mass. The front slope is very small, generally below 1/250, covering a wide area. Meteorological factors such as temperature, sunshine, wind and relative humidity on both sides of the front are obviously discontinuous, and the weather characteristics are quite different. Most parts of Yunnan, located on the southwest side of the front, are controlled by a single warm air flow, with blue sky, bright sunshine and high temperature. For example, the average temperature in Kunming in June 5438+10 was 7.7℃, and there was no severe cold in winter. Most of Liangshan Prefecture, Sichuan, Northeast Yunnan and Guizhou under the front are located on the cold air side, with northerly winds and low temperatures. For example, in June 5438+10/October, the average temperature in Guiyang was 5.0℃, and it rained continuously; The number of days of precipitation ≥ 0. 1mm per month is more than/kloc-0 ~15 days, so it is said that there are no three sunny days.
When the cold air is strong and the front is located to the west of Kunming, the eastern part of Yunnan is below the static front, the temperature drops suddenly, and the weather turns cloudy or there is light rain. Therefore, there is also a saying in Yunnan that "there is no cold and heat in the four seasons, and it will become autumn when it rains". This front is the northern boundary of the dry and warm continental air mass that controls Yunnan, and it is also the northern boundary of the monsoon climate in Yunnan. During this period, northeastern Yunnan and most parts of Guizhou were controlled by cold air moving at mid-latitude. Now take Kunming and Guiyang as representatives to illustrate their differences.
First of all, the four seasons in Kunming are not clear. According to the standard of dividing the four seasons proposed by Mr. Zhang Baokun (that is, the average temperature of 22℃ is summer), as can be seen from Figure 4, there is no summer in Kunming all year round, and spring and autumn are connected, which lasts for 9 months and has about 3 months of winter. Guiyang has four distinct seasons.
Secondly, Kunming has the characteristics of small temperature annual range and large daily range; In Guiyang, however, the annual range is larger, and the daily range is smaller (table 1).
Third, the dry and wet seasons in Kunming are more distinct than those in Guiyang. As can be seen from Table 2, the dry season in Kunming is from June to April, and the precipitation only accounts for 1 1.2% of the whole year. The precipitation ≥0. 1mm is only 3 1 day, 50 days less than Guiyang, and the relative humidity is 66% less than rainy season.