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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 ...
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.
[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.
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.
A practical definition of water pollution is: "Water pollution is the addition of substances or energy forms that directly or indirectly alter the nature of the water body in such a manner that negatively affects its legitimate uses." [1]: 6 Water is typically referred to as polluted when it is impaired by anthropogenic contaminants.
Even though approximately 70% of the Earth's surface consists of water, more than 75% of the water exchange between the Earth's surface and the atmosphere occurs over the oceans. The ocean absorbs part of the energy from sunlight as heat and is initially absorbed by the surface. [13] Eventually a part of this heat also spreads to deeper water.
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 study of hydrodynamic stability aims to find out if a given flow is stable or unstable, and if so, how these instabilities will cause the development of turbulence. [1] The foundations of hydrodynamic stability, both theoretical and experimental, were laid most notably by Helmholtz , Kelvin , Rayleigh and Reynolds during the nineteenth ...