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Adiabatic processes for air have a characteristic temperature-pressure curve. As air circulates vertically, the air takes on that characteristic gradient. When the air contains little water, this lapse rate is known as the dry adiabatic lapse rate: the rate of temperature decrease is 9.8 °C/km (5.4 °F per 1,000 ft) (3.0 °C/1,000 ft). The ...
The vadose zone, also termed the unsaturated zone, is the part of Earth between the land surface and the top of the phreatic zone, the position at which the groundwater (the water in the soil's pores) is at atmospheric pressure ("vadose" is from the Latin word for "shallow").
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 feet (300 m). The moist adiabatic lapse rate varies from 1.1 to 2.8 °C (2.0 to 5.0 °F) per 1,000 vertical feet (300 m).
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.
The virtual temperature of unsaturated moist air is always greater than the absolute air temperature, however, as the existence of suspended cloud droplets reduces the virtual temperature. The virtual temperature effect is also known as the vapor buoyancy effect. [2]
Dew point, which is a temperature that occurs when atmospheric relative humidity reaches 100% and the air is saturated with moisture; Saturated absorption, a set-up that enables the precise determination of the transition frequency of an atom between its ground state and an optically excited state
After the clouds have risen, a rain-cooled layer remains. The cluster shoots a burst of unsaturated air down towards the ground. In doing so, the system loses all of its updraft-related fuel. [6] The raindrops begin to evaporate into dry air, which reinforces the effects of the heat burst (evaporation cools the air, increasing its density).
The concept of potential temperature applies to any stratified fluid. It is most frequently used in the atmospheric sciences and oceanography. [2] The reason that it is used in both fields is that changes in pressure can result in warmer fluid residing under colder fluid – examples being dropping air temperature with altitude and increasing water temperature with depth in very deep ocean ...