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In numerous fields of study, the component of instability within a system is generally characterized by some of the outputs or internal states growing without bounds...
is a condition where the atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
is generally considered to be unstable and as a result the weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
is subject to a high degree of variability through distance and time . Atmospheric stability is a measure of the atmosphere's tendency to encourage or deter vertical motion, and vertical motion is directly correlated to different types of weather systems and their severeties. In unstable conditions, a lifted parcel of air will be warmer than the surrounding air at altitude. Because it is warmer, it is less dense and is prone to further ascent. In meteorology, instability is described by a lifted index and a K-index.
There are two primary forms of atmospheric instability:
- Convective Instability
In meteorology, convective instability or stability of an airmass refers to its ability to resist vertical motion. A stable atmosphere makes vertical movement difficult, and small vertical disturbances dampen out and disappear...
Under convective instability
thermal mixing through convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
in the form of warm air rising leads to the development of clouds and possibly precipitation
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...
or convective storms.
is produced through the horizontal movement of air and the physical forces it is subjected to such as the Coriolis force and pressure gradient force
The pressure gradient force is not actually a 'force' but the acceleration of air due to pressure difference . It is usually responsible for accelerating a parcel of air from a high atmospheric pressure region to a low pressure region, resulting in wind...
. Dynamic lifting and mixing produces cloud, precipitation and storms often on a synoptic scale
The synoptic scale in meteorology is a horizontal length scale of the order of 1000 kilometres or more. This corresponds to a horizontal scale typical of mid-latitude depressions...