Why is there water vapor in the air? Looks like an idiot.

There is water vapor in the air, which mainly comes from the evaporation of water on the earth's surface. It is produced by the air flow in the troposphere, the atmosphere on the earth's surface. The earth's atmosphere can be divided into several layers according to its basic characteristics. According to the characteristics of atmospheric temperature distribution with height, people can divide the atmosphere into troposphere, stratosphere, mesosphere, thermosphere and escape layer.

The "troposphere" of the earth is located at the bottom of the atmosphere, which concentrates about 75% of the atmospheric mass and more than 90% of the water vapor mass. Its lower bound is connected with the ground, its upper bound height varies with geographical latitude and season, and its height varies with latitude. The average height in low latitudes is 17 ~ 18 km, in mid latitudes it is 10 ~ 12 km, and in polar regions it is 8 ~ 9 km, which is higher in summer than in winter.

In the troposphere, the temperature decreases with the elevation, and increases by 100 m on average. The temperature dropped by about 0.65℃. Is it because the main heat source of troposphere atmosphere is the ground, so the temperature decreases with the increase of height? Long wave radiation, the higher from the ground, the less heated and the lower the temperature. Due to the great influence of the surface, the horizontal distribution of meteorological elements (temperature, humidity, etc.). ) uneven. The regular vertical movement of air and the irregular turbulence are quite intense. The water vapor, dust and heat in the upper and lower layers are exchanged and mixed. Because more than 90% of the water vapor is concentrated in the troposphere, it is cloudy, foggy, rainy and snowy? All weather phenomena occur in the troposphere. This is the main reason why water vapor exists in the air.