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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 ...
[clarification needed] [1] Atmospheric instability encourages vertical motion, which is directly correlated to different types of weather systems and their severity. For example, under unstable conditions, a lifted parcel of air will find cooler and denser surrounding air, making the parcel prone to further ascent, in a positive feedback loop.
For example, air and water; both are fluids and if we consider them together then they can be seen as a stratified fluid system. Density variations in the atmosphere profoundly affect the motion of water and air. Wave phenomena in air flow over the mountains and occurrence of smog are the examples of stratification effect in the atmosphere.
The saturated adiabatic lapse rate (SALR), or moist adiabatic lapse rate (MALR), is the decrease in temperature of a parcel of water-saturated air that rises in the atmosphere. It varies with the temperature and pressure of the parcel and is often in the range 3.6 to 9.2 °C/km (2 to 5 °F/1000 ft ), as obtained from the International Civil ...
If the air parcel is pushed up and =, the air parcel will not move any further. If the air parcel is pushed up and N 2 < 0 {\displaystyle N^{2}<0} , (i.e. the Brunt–Väisälä frequency is imaginary), then the air parcel will rise and rise unless N 2 {\displaystyle N^{2}} becomes positive or zero again further up in the atmosphere.
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.
The effects are even more pronounced when a city is surrounded by hills or mountains since they form an additional barrier to air circulation. During a severe inversion, trapped air pollutants form a brownish haze that can cause respiratory problems. The Great Smog of 1952 in London, England, is one of the most serious examples of such an ...
Dry air does not have as much water vapor, therefore dry air cools at a higher rate with vertical movement than moist air. 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 ...