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Why does most weather occur in the troposphere?

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Weather forecasting Doppler radars, such as this one operated by the U.S. National Weather Service at New Underwood, South Dakota, extract the Doppler frequency shift of the echo produced by a moving target by noting how much the frequency of the received signal differs from the frequency of the signal that was transmitted.

The troposphere is the lowest region of the atmosphere, extending from the Earth's surface to the tropopause. Most weather occurs within this layer primarily because it contains the vast majority of the atmosphere's water vapor and is characterized by vigorous convective mixing.213

This layer is the site of active convection, where rising parcels of air expand and cool due to decreasing atmospheric pressure. As this air cools, water vapor condenses to form clouds and precipitation, which are the fundamental components of weather systems.3425

Furthermore, the troposphere is capped by the tropopause, a region of stable thermal layering that inhibits vertical motion into the stratosphere. Because upward movement is constrained by this stable boundary, weather-related processes—such as the formation of cumulonimbus clouds and large-scale circulation patterns like the Hadley cell—are effectively contained within the troposphere.3