Why do weather changes only occur in the troposphere?

The troposphere is the layer of the earth's atmosphere near the ground. At the same time, it is also the densest layer in the earth's atmosphere, containing about 75% of the mass of the whole atmosphere and almost all the water vapor and aerosol.

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 water vapor is concentrated in the troposphere, many weather phenomena such as clouds, fog, rain and snow occur in the troposphere.