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Theta-e and theta-w


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  • Location: South Norfolk, 44 m ASL.
  • Weather Preferences: Varied and not extreme.
  • Location: South Norfolk, 44 m ASL.
    Posted (edited)

    Can anyone possibly explain the difference between these two measures and their relevance to atmospheric instability, please?  I've read articles online on theta-e but they make it sound so, for the want of a better word, random - take this parcel of air, raise it, lower it, cool it, warm it, add it to a Sunday roast and you can calculate something that roughly equates to dewpoint is about all I understood of them!  Theta-w is, I understand, based on the wet-bulb temperature, and therefore is also related to dewpoint in the sense that moister air will have a wet bulb temperature closer to that of the dry bulb value to to a lack of evaporative cooling.

    Cheers!

    Edited by chrisbell-nottheweatherman
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    Posted
  • Location: Tonbridge,Kent
  • Location: Tonbridge,Kent
    On 16/05/2022 at 18:39, chrisbell-nottheweatherman said:

    Can anyone possibly explain the difference between these two measures and their relevance to atmospheric instability, please?  I've read articles online on theta-e but they make it sound so, for the want of a better word, random - take this parcel of air, raise it, lower it, cool it, warm it, add it to a Sunday roast and you can calculate something that roughly equates to dewpoint is about all I understood of them!  Theta-w is, I understand, based on the wet-bulb temperature, and therefore is also related to dewpoint in the sense that moister air will have a wet bulb temperature closer to that of the dry bulb value to to a lack of evaporative cooling.

    Cheers!

    Its really then an sum of expectation,how quick a certain level can be mixed out going by the model predicting it,unless we had our own weather balloons and equation as such ....ide say theta- e was the apollo,theta -w  was the old vic,in my  guide book anyhow  :-》

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    Posted
  • Location: Woodchurch, Kent.
  • Weather Preferences: Thunderstorm.
  • Location: Woodchurch, Kent.
    On 16/05/2022 at 18:39, chrisbell-nottheweatherman said:

    Can anyone possibly explain the difference between these two measures and their relevance to atmospheric instability, please?  I've read articles online on theta-e but they make it sound so, for the want of a better word, random - take this parcel of air, raise it, lower it, cool it, warm it, add it to a Sunday roast and you can calculate something that roughly equates to dewpoint is about all I understood of them!  Theta-w is, I understand, based on the wet-bulb temperature, and therefore is also related to dewpoint in the sense that moister air will have a wet bulb temperature closer to that of the dry bulb value to to a lack of evaporative cooling.

    Cheers!

    "Theta-E is a quantity that indicates the stability of the atmosphere, or the available energy in the atmosphere. In general, larger Theta-E values represent greater potential instability. Theta-E is the temperature the air would have if (1) all of the moisture were condensed out and (2) it was lowered to sea level."

    Theta-E is easier to understand than Theta-W but if its warm it doesn't necessarily mean Storm production happens as it also needs other things in the air.

    "The wet-bulb potential temperature is identical to the wet-bulb temperature, except that the sample is brought moist adiabatically from the wet-bulb temperature at the initial level to the wet-bulb potential temperature at the 1000-hPa level"

    Theta-W is very confusing but all you really need to know is that when you get Theta-W air rises and condenses at an elevated level but I don't know why or how, I'm still confused about that one to be honest,I have an idea but I'm not too sure about how correct it is.

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  • Location: South Norfolk, 44 m ASL.
  • Weather Preferences: Varied and not extreme.
  • Location: South Norfolk, 44 m ASL.

    Presumably, if a parcel of air would still be warm after water condenses out and it has dropped to sea level, it means that, in its native state, it's warm and moist, and is therefore unstable?  Theta-W still confuses me, though.  If it's the same as wet bulb temperature , then why use it instead?

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