NationMaster - Encyclopedia: Equivalent potential temperature

Equivalent potential temperature, commonly referred to as Theta-e $left( theta_e right)$ , is a measure of the instability of air at a given pressure, humidity, and temperature. Theta-e is the temperature of one parcel of air at 100 kPa (1000 mbar) after considering the energy from when the water vapor in the parcel is condensed. The pascal (symbol Pa) is the SI unit of pressure. ... A millibar (mbar, also mb) is 1/1000th of a bar, a unit for measurement of pressure. ...

Theoretically, it would be the temperature of the parcel if the following procedure were performed:

Lift adiabatically (pressure drop, and drop in temperature, but no change in heat) until it becomes saturated with water vapor,
Allow all the water vapor to condense out, releasing its latent heat, and
Drop the parcel adiabatically (pressure rise but no change in heat content) to an atmospheric pressure of 1000 millibars.

This resulting allows the comparison of parcels of air at different pressures, and is a measure of the instability of that air. [1] In thermodynamics, an adiabatic process is a process in which no heat is transferred to or from working fluid. ... Water vapor, also aqueous vapor, is the gas phase of water. ... Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ...

The formula for theta-e is the following:[2]

$theta_e = T_e left( frac{p_0}{p} right)^frac{R}{c_p} approx left( T + frac {l_v}{c_{p}} r right) left( frac{p_0}{p} right)^frac{R}{c_p}$

Where:

$T e$ = equivalent temperature
T = Temperature of air at pressure p
$p$ = pressure at the point (mbar)
$p 0$ = standard reference pressure (1000 mbar)
$R$ = specific gas constant for air (287 J/(kg·K))
$c p$ = specific heat of dry air at constant pressure (1004 J/(kg·K))
$l v$ = latent heat of evaporation ((2400 kJ/kg {at 25C} to 2600 kJ/kg {at -40C})
r = mixing ratio of water vapor in air

Equivalent temperature is the temperature of an air parcel from which we would have completely extracted its water vapor content by an adiabatic process. ... This article or section does not cite its references or sources. ... The parts-per notations are used to denote extremely low concentrations of chemical elements. ...

Bibliography

M K Yau and R.R. Rogers, Short Course in Cloud Physics, Third Edition, published by Butterworth-Heinemann, January 1, 1989, 304 pages. EAN 9780750632157 ISBN 0-7506-3215-1

Meteorological data and variables

Atmospheric pressure | Baroclinity | Cloud | Convection | CAPE | CIN | Dew point | Heat index | Humidex | Humidity | Lightning | Pot T | Precipitation | Sea surface temperature | Surface solar radiation | Surface weather analysis | Temperature | Theta-e | Visibility | Vorticity | Wind chill | Water vapor | Wind January 1 is the first day of the calendar year in both the Julian and Gregorian calendars. ... 1989 (MCMLXXXIX) was a common year starting on Sunday of the Gregorian calendar. ... Satellite image of Hurricane Hugo with a polar low visible at the top of the image. ... Diurnal (daily) rhythm of air pressure in northern Germany (black curve is air pressure) Atmospheric pressure is the pressure at any point in the Earths atmosphere. ... It has been suggested that Baroclinic instability and Baroclinic vector be merged into this article or section. ... Cumulonimbus capillatus incus floating over Swifts Creek, Victoria in Australia A cloud is a visible mass of condensed droplets or frozen crystals suspended in the atmosphere above the surface of the Earth or another planetary body. ... Convection is the internal movement of currents within fluids (i. ... In meteorology, convective available potential energy (CAPE) is the amount of energy a parcel of air would have if lifted a certain distance vertically through the atmosphere. ... Convective inhibition (CIN or CINH) is a meteorlogic parameter that measures the amount of energy that will prevent an air parcel from rising from the surface to the level of free convection. ... Dew on a spider web The dew point or dewpoint of a given parcel of air is the temperature to which the parcel must be cooled, at constant barometric pressure, for the water vapor component to condense into water, called dew. ... The heat index (HI) or humidex is an index that combines air temperature and relative humidity to determine an apparent temperature â€” how hot it actually feels. ... Heat Index (HI) is an index that combines air temperature and relative humidity to determine an apparent temperature — how hot it actually feels. ... Humidity is the concentration of water vapor in the air. ... Lightning is an atmospheric discharge of electricity, usually, but not always, during a rain storm. ... The potential temperature of a parcel of air at pressure is the temperature that the parcel would acquire if adiabatically brought to a standard reference pressure , usually 1 bar. ... Visualisation of the SST of the ocean just before Hurricane Bob (August 14, 1991) Sea surface temperature (SST) is the water temperature at 1 meter below the sea surface. ... Solar irradiance spectrum at top of atmosphere. ... A surface weather analysis for the United States on October 21, 2006. ... Fig. ... In meteorology, visibility is a measure of the distance that can be seen clearly at any given time. ... Vorticity is a mathematical concept used in fluid dynamics. ... Wind chill is the apparent temperature felt on the exposed human (or animal) body due to the combination of air temperature and wind speed. ... Water vapor, also aqueous vapor, is the gas phase of water. ... Wind is the rough horizontal movement of air (as opposed to an air current) caused by uneven heating of the Earths surface. ...

External links

Source material: http://meted.ucar.edu/awips/validate/thetae.htm

Categories: Atmospheric science stubs | Atmospheric thermodynamics

Results from FactBites:

Temperature - Wikipedia, the free encyclopedia (3046 words)
	Temperature is a physical property of a system that underlies the common notions of "hot" and "cold", in which something that is hotter has the greater temperature.
	Temperature arises from the random microscopic motions of the atomic and subatomic constituents of matter, where temperature is related to the average energy of these microscopic motions.
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Equivalent potential temperature - Wikipedia, the free encyclopedia (253 words)
	Equivalent potential temperature, commonly referred to as Theta-e
	, is a measure of the instability of air at a given pressure, humidity, and temperature.
	Theta-e is the temperature of one parcel of air at 100 kPa (1000 mbar) after considering the energy from when the water vapor in the parcel is condensed.

More results at FactBites »

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