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!