Question about mixed-layer parcel properties

[Chun-ChihWang]

This is somewhat related to the mixed-layer parcel definition problems I mentioned in another post, but this one is about the computation of the mixed-layer parcel itself. In sharptab.params,

"
def __ml(self, prof, **kwargs):
'''
Create a mixed-layer parcel with mixing within the lowest XXX hPa,
where XXX is supplied. Default is 100 hPa.
If
'''
self.desc = '%.2f hPa Mixed Layer Parcel' % self.presval
pbot = kwargs.get('pbot', prof.pres[prof.sfc])
ptop = pbot - self.presval
self.pres = pbot
mtheta = mean_theta(prof, pbot, ptop, exact=True)
self.tmpc = thermo.theta(1000., mtheta, self.pres)
mmr = mean_mixratio(prof, pbot, ptop, exact=True)
self.dwpc = thermo.temp_at_mixrat(mmr, self.pres)
"

The temperature of the mixed-layer parcel is derived by reverting the layer-averaged potential temperature to the parcel bottom (or surface) pressure. However, I found that this results in a warmer parcel starting temperature the deeper the layer I average. That is, my parcel starting temperature is going to be HIGHER if I average over the lowest 200 mb than if I average over the lowest 100 mb, since the potential temperature normally increases with altitude. Is this the correct behavior?

The mixed-layer parcel starting dew point calculation looks OK to me.

David