why does most weather occur in one layer of the atmosphere?

Answer 1

Simple answer: it has the most volatile mixing of air of any of the layers.

For example, the sun heats the ground layer of the Earth. This warm air rises through the cooler air around it and forms clouds. Given the right conditions, these clouds can form rain showers, snow showers, thunderstorms, etc.

The higher level of the atmosphere, for the most part, have either a mostly constant temperature, or a temperature that gets slowly warmer (basically a "cap" that prevents cloud formation). Plus, there is nothing to absorb the sun's heat.

Answer 2

The main reason is the presence of water vapour which plays an important part in the formation of many weather systems.The moisture(presence of water vapour) is mainly confined to the troposphere.The moisture content usually becomes less as we go up because of the cold temperature at higher levels.Warm air can hold more moisture than cold air.So,cold air at higher levels can hold very little moisture only.So the amount of water vapour becomes very less beyond certain height.
Moreover,above tropopause,the temperature starts increasing and the air becomes more stable preventing the formation of clouds.
Due to the above reasons,most weather systems are confined to the troposphere only.

Answer 3

Most of the OBSERVABLE weather occurs in the troposphere; half of the air is in that one zone. Going higher into the atmosphere makes it more difficult for air-borne particles (everything from dust to pollution to water droplets) to remain airborne, so they basically stay at lower elevations in the atmosphere.
In the higher reaches, there is much occuring...meterorites, gamma rays, electro-magnetic storms, don't forget the Northern Lights...