Cyclones and Carnot cycle

[Hydraulics]

Could anyone explain me the analogy Cyclone - Carnot engine? (Emanuel, 1991). I mean, which are the isotherm and adiabatic traks of the Carnot cycle in a cyclone? Thanks!

The first branch is along ocean surface, an isotherm with air moving inward; the second leg is an adiabatic expansion, with air first ascending and then flowing outward; the third is again an isotherm with air descending slowly; the fourth contributes little to the thermodinamic cycle.

You can find the original paper here (pdf, 950 kB), with a formal definition of the efficiency.

Hope it helps.