Definitions for "Equivalent Potential Temperature"
The temperature a parcel of air would have if it is lifted until it became saturated, all water vapour is condensed out, and returned adiabatically (i.e., without transfer of heat or mass) to a pressure of 1000 millibars. Equivalent Potential Temperature, typically expressed in degrees Kelvin, is directly related to the amount of heat present in an air parcel. Thus, it is useful in diagnosing atmospheric instability. Same as Theta e.
the temperature parcel of air would have if a) it was lifted until it became saturated, b) all water vapor was condensed out, and c) it was returned adiabatically (i.e., without transfer of heat or mass) to a pressure of 1000 millibars. Theta-e, which typically is expressed in degrees Kelvin, is directly related to the amount of heat and moisture present in an air parcel. Thus, it is useful in diagnosing atmospheric instability.
The equivalent potential temperature is the temperature a parcel at a specific pressure level and temperature would have if it were raised to 0 mb, condensing all moisture from the parcel, and then lowered to 1000 mb.