Dictionary - Definition of EQUIVALENT TEMPERATURE

Specialty Expressions: EQUIVALENT TEMPERATURE

Expressions

Domain

Definition

British equivalent temperature

Mining

See: equivalent temperature. (references)

Equivalent temperature

Aerospace

1. Isobaric equivalent temperature; the temperature that an air parcel would have if all water vapor were condensed out at constant pressure, the latent heat released being used to heat the air, Ti, e = T [1 + (Lw / cp T)] where Ti, e is the isobaric equivalent temperature; T is the temperature; w is the mixing ratio; L is the latent heat; and cp is the specific heat of air at constant pressure. 2. Adiabatic equivalent temperature; The temperature that an air parcel would have after undergoing the following (physically unrealizable) process: dry-adiabatic expansion until saturated; pseudoadiabatic expansion until all moisture is precipitated out; dry-adiabatic compression to the initial pressure. This is the equivalent temperature as read from a thermodynamic chart and is always greater than the isobaric equivalent temperature: Ta, e = T exp (Lw / cp T) where Ta, e is the adiabatic equivalent temperature. Also called pseudoequivalent temperature. (references)

Equivalent temperature

Mining

A composite of mean radiant temperature and air temperature; also defined as the mean temperature of the environment effective in controlling the rate of sensible heat loss from a black body in still air when the surface temperature and size of the black body are comparable to those of the human body. Where the enclosure surface (mean radiant temperature) and air temperatures are equal, this temperature is also the British equivalent temperature; when not equal, the British equivalent temperature is that temperature at which a body with an 80 degrees F (26.7 degrees C) surface temperature will lose sensible heat at the same rate as in the given environment. Syn: British equivalent temperature. (references)

Isobaric equivalent temperature

Aerospace

See equivalent temperature, sense 1. (references)

Isobaric equivalent temperature

Physics

Temperature that an air parcel would have if all water vapor were condensed out at constant pressure, the latent heat released being used to heat the air. Source: European Union. (references)

Source: compiled by the editor from various references; see credits.

Top

Extended Definition: Equivalent temperature

Equivalent temperature

Equivalent temperature is the temperature of an air parcel from which we would have completely extracted its water vapor content by an adiabatic process.

Air contains water vapor that has been evaporated into it from liquid sources (lakes, sea, etc...). The energy needed to do that has been taken from the air. Taking a volume of air at temperature T and mixing ratio of r , drying it by condensation will restitute energy to the airmass. This will depend on the latent heat release as:

$T_e \approx T + \frac {L_v}{c_{pd}}$ r

$\,L_v$ : latent heat of evaporation (2400 kJ/kg {at 25C} to 2600 kJ/kg {at -40C})

$\,c_{pd}$ : specific heat at constant pressure for air ( $\approx$ 1004 J/(kg·K))

Tables exist for exact values of the last two coefficients.

Bibliographie

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

J.V. Iribarne and W.L. Godson, Atmospheric Thermodynamics, published by D. Reidel Publishing Company, Dordrecht, Holland, 1973, 222 pages

Meteorological data and variables

General	Adiabatic processes · Lapse rate · Lightning · Surface solar radiation · Surface weather analysis · Visibility · Vorticity · Wind

Condensation	Cloud · Cloud condensation nuclei · Fog · Precipitation · Water vapor

Convection	Convective available potential energy (CAPE) · Convective inhibition (CIN) · Convective instability · Convective temperature (T_c) · Helicity · Lifted index (LI)

Temperature	Dew point (T_d) · Equivalent temperature (T_e) · Heat index · Humidex · Humidity · Potential temperature (θ) · Equivalent potential temperature (θ_e) · Sea surface temperature (SST) · Wet-bulb temperature · Wind chill

Pressure	Atmospheric pressure · Baroclinity

Source: adapted by the editor from Wikipedia, the free encyclopedia; from the article "Equivalent temperature". Image Credit.