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It is a form of fluid instability found in thermally stratified atmospheres in which a colder fluid overlies a warmer one. When an air mass is unstable, the element of the air mass that is displaced upwards is accelerated by the pressure differential between the displaced air and the ambient air at the (higher) altitude to which it was displaced.
In unstable stratification, on the other hand, buoyancy forces cause convection. The less-dense layers rise though the denser layers above, and the denser layers sink though the less-dense layers below. Stratifications can become more or less stable if layers change density. The processes involved are important in many science and engineering ...
As a result of the latent heat that is released during water vapor condensation, moist air has a relatively lower adiabatic lapse rate than dry air. This makes moist air generally less stable than dry air (see convective available potential energy [CAPE]). The dry adiabatic lapse rate (for unsaturated air) is 3 °C (5.4 °F) per 1,000 vertical ...
A third source of lift is wind circulation forcing air over a physical barrier such as a mountain (orographic lift). [10] If the air is generally stable, nothing more than lenticular cap clouds will form. However, if the air becomes sufficiently moist and unstable, orographic showers or thunderstorms may appear. [18]
Weather radar loop showing intense snow bands (lighter color) due to CSI ahead of a warm front.. Conditional symmetric instability, or CSI, is a form of convective instability in a fluid subject to temperature differences in a uniform rotation frame of reference while it is thermally stable in the vertical and dynamically in the horizontal (inertial stability).
There are five types of air pollution dispersion models, as well as some hybrids of the five types: [1] Box model – The box model is the simplest of the model types. [2] It assumes the airshed (i.e., a given volume of atmospheric air in a geographical region) is in the shape of a box.
If the acceleration is back towards the initial position, the stratification is said to be stable and the parcel oscillates vertically. In this case, N 2 > 0 and the angular frequency of oscillation is given N. If the acceleration is away from the initial position (N 2 < 0), the stratification is unstable. In this case, overturning or ...
The most important feature of baroclinic instability is that it exists even in the situation of rapid rotation (small Rossby number) and strong stable stratification (large Richardson's number) typically observed in the atmosphere. [citation needed] The energy source for baroclinic instability is the potential energy in the environmental flow.