The thermodynamic cycles and associated energetics of Hurricane Edouard (2014) during its intensification

This study expands on a previous analysis of the intensification of Hurricane Edouard (2014) in the isentropic coordinates to further examine the thermodynamic processes that lead to the strengthening of the storm. Thermodynamic cycles are extracted using the methodology known as the Mean Airflow as Lagrangian Dynamics Approximation. The most intense thermodynamic cycle here is associated with the air rising within the hurricane eyewall. Its structure remains mostly steady during the early development of Edouard but evolves rapidly as the storm intensifies. Through intensification, the ascent shifts toward high values of entropy under the effect of enhanced surface heat fluxes and stronger surface winds, while reaching higher altitudes and lower temperatures. The near-rapid intensification onset of Edouard corresponds to an increase in the energy input into the cycle and an increase in the amount of kinetic energy generated. The external heating fluctuates considerably in the two low-level legs with a period of about 16-24 h, indicative of diurnal variation in the thermodynamic cycle. During the intensification of Edouard, the mechanical work production and the Carnot efficiency both increase dramatically, which can be attributed to the increase in energy transport and deepening of the thermodynamic cycle. In addition, there is a substantial increase of the mechanical work done during the horizontal expansion of air parcels near Earth's surface, and a larger fraction of the kinetic energy generated is used to sustain and intensify the horizontal flow rather than to provide a vertical acceleration in the updrafts.