Isentropic coordinates

Because, in a stably stratified atmosphere, the potential temperature increases monotonically with height, it is often used as the vertical coordinate in atmospheric problems. Such a system is called the isentropic coordinate system because a constant 0 surface corresponds to a surface of constant entropy S (0) = cp In 0 + constant. In this framework, the vertical velocity... 

As indicated earlier, atmospheric motions are often advantageously represented in an isentropic coordinate system. In this case, Ertel s potential vorticity is defined by... 

Tung, K.K., On the two-dimensional transport of stratospheric trace gases in isentropic coordinates. J Atmos Set 39, 2330, 1982. 

Ko, M. K. W., K. K. Tung, D. K. Weisenstein, and N. D. Sze (1985). A Zonal-mean model of stratospheric trace transport in isentropic coordinators numerical simulation for nitrous oxide and nitric acid. J. Geophys. Res. 90, 2313-2329. 

Although the T-s diagram is veiy useful for thermodynamic analysis, the pressure enthalpy diagram is used much more in refrigeration practice due to the fact that both evaporation and condensation are isobaric processes so that heat exchanged is equal to enthalpy difference A( = Ah. For the ideal, isentropic compression, the work could be also presented as enthalpy difference AW = Ah. The vapor compression cycle (Ranldne) is presented in Fig. H-73 in p-h coordinates. 

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