The troposphere is located in the lowest layer of the atmosphere and stretches from the earth's surface to the upper air to the top of the troposphere, the starting point of the stratosphere. The average thickness is about 12 kilometers, and its thickness varies. Its thickness is 8 kilometers above the earth’s poles and 17 kilometers above the equator. It is the densest layer in the atmosphere, concentrating about 75% of the atmospheric mass and 90% The above water vapor quality. Its lower bound is connected to the ground, and the upper bound height varies with geographic latitude and seasons. Its height varies with latitude, with an average height of 17-18 kilometers in low latitudes, 10-12 kilometers in mid-latitudes, and 8-9 kilometers in high latitudes, and summer is higher than winter.
2. Features:
(1) The temperature decreases with the increase in altitude: this is because the layer cannot directly absorb the short-wave radiation of the sun, but can absorb the long-wave radiation reflected by the ground to heat the atmosphere from the underlying surface. Therefore, the air near the ground is heated more, and the air far away from the ground is less heated. For every one kilometer rise, the temperature drops by about 6.5 degrees.
(2) Air convection: Because the surface of the lithosphere and hydrosphere is heated by the sun, and the lower layer of air is heated by thermal radiation, the cold and hot air undergoes vertical convection, and the ground is divided into land and sea, day and night, and latitude. Therefore, the temperature in different areas is also different, which forms the horizontal movement of air.
(3) The horizontal distribution of various elements such as temperature and humidity is uneven: the atmosphere is in contact with the surface, and water vapor, dust, microorganisms and toxic substances produced by human activities enter the air layer. Therefore, in addition to the vertical and horizontal movement of the airflow, the chemical The process is very active, and as the air mass becomes cold or hot, water vapor forms a series of weather phenomena such as rain, snow, hail, frost, dew, cloud, and fog.