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Atmospheric instability is a condition where the Earth's atmosphere is considered to be unstable and as a result local weather is highly variable through distance and time. [ clarification needed ] [ 1 ] Atmospheric instability encourages vertical motion, which is directly correlated to different types of weather systems and their severity.
A stable atmosphere makes vertical movement difficult, and small vertical disturbances dampen out and disappear. In an unstable atmosphere, vertical air movements (such as in orographic lifting , where an air mass is displaced upwards as it is blown by wind up the rising slope of a mountain range) tend to become larger, resulting in turbulent ...
Stable stratification of fluids occurs when each layer is less dense than the one below it. Unstable stratification is when each layer is denser than the one below it. Buoyancy forces tend to preserve stable stratification; the higher layers float on the lower ones. In unstable stratification, on the other hand, buoyancy forces cause convection ...
By contrast, other conditions, such as a less warm air parcel or a parcel in an atmosphere with a temperature inversion (in which the temperature increases above a certain height) have much less capacity to support vigorous upward air movement, thus the potential energy level (CAPE) would be much lower, as would the probability of thunderstorms.
Atmospheric stability occurring at night with radiative cooling tends to vertically constrain turbulent eddies, thus increasing the wind gradient. [8] The magnitude of the wind gradient is largely influenced by the weather, principally atmospheric stability and the height of any convective boundary layer or capping inversion.
So cool air lying on top of warm air can be stable, as long as the temperature decrease with height is less than the adiabatic lapse rate; the dynamically important quantity is not the temperature, but the potential temperature—the temperature the air would have if it were brought adiabatically to a reference pressure. The air around the ...
The lunar atmosphere is extremely thin and technically classified as an exosphere, meaning atoms do not collide with each other because their numbers are so sparse, in contrast to Earth's thick ...
Density stratification has significant effect on diffusion in fluids. For example, smoke which is coming from a chimney diffuses turbulently if the earth atmosphere is not stably stratified. When the lower air is in stable condition, as in morning or early evening, the smoke comes out and become flat into a long, thin layer.