Reconstruction of thermodynamic cycles in a high-resolution simulation of a hurricane

The relationship between energy transport and kinetic energy generation in a hurricane is analyzed. The hydrological cycle has a negative impact on the generation of kinetic energy. First, in a precipitating atmosphere, mechanical work must also be expended in order to lift water. Second, the injection of water vapor at low relative humidity and its removal through condensation and precipitation reduces the ability of a thermodynamic cycle to generate work. This reduction can be directly quantified in terms of the change in the Gibbs free energy between the water added and removed. Anewly developed approach-namely, themean airflow as Lagrangian dynamics approximation-is used to extract thermodynamic cycles from the standard output of a numerical simulation of a hurricane. While convection in the outer rainbands is inefficient at producing kinetic energy, the deepest overturning circulation associated with the rising air within the eyewall is an efficient heat engine that produces about 70% as much kinetic energy as a comparable Carnot cycle. This confirms that thermodynamic processes play a central role in hurricane formation and intensification and that the thermodynamic cycles in a hurricane are characterized by high generation of kinetic energy that differ significantly from those found in atmospheric convection.