Isentropic Surfaces

Unsaturated air parcels move along isentropic surfaces thus allowing a conceptually easy way to identify airstreams and to visualize regions of rising and sinking air. However, the convenience of isentropic analysis is diminished when latent heat is released by the condensation of moisture. The release of latent heat in an ascending saturated air parcel causes the parcel to leave the isentropic surface and to move upward with respect to the surface (Moore 1993, p. 9)