Theta as a Vertical Coordinate
q = T (1000/P)k , where k= Rd / Cp
Entropy = ? = Cp lnq + const
If ? = const then q = const, so constant entropy sfc = isentropic sfc
Three types of stability, since dq/ dz = (q /T) [?d - ?]
- stable: ? < ?d, q increases with height
- neutral: ? = ? d, q is constant with height
- unstable: ? > ? d, q decreases with height
So, isentropic surfaces are closer together in the vertical in stable air and further apart in less stable air.