Re: More on Theta E


"Joe Egginton" <joe.egginton@xxxxxxxxxx> wrote in message
news:3m0vf8F14manqU1@xxxxxxxxxxxxxxxxx
> Hello All,
>
> I'm confused over what Theta E is measuring.
>
> Does it measure the temperature of an airmass, or the temperature of a
> parcel of air that is rising?
>
> Joe
> Wolverhampton
> 175m asl

T_e is the equivalent temperature. Effectively this the temperature that a
parcel of moist air would achieve if it were lifted cooling at the saturated
adiabatic lapse rate (SALR) until it is so cold that the vapour pressure is
effectively zero and all water vapour is precipitated and then brought back
down to the same level warming at the dry adiabatic lapse rate (DALR).

For theta_e is potential equivalent temperature at a standard pressure
level, usually 1000hPa, so assuming you began at a higher level than
1000hPa, you simply continue to warm the parcel at the DALR until you reach
1000hPa.

The lapse rate of theta_e will tell you something about the stability of the
atmosphere. Slightly simplistically, a decrease with height implies an
unstable layer, an increase with height, a stable layer. Theta_e should be
pretty much constant with height within a convective cloud.



.

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