The efficiency of diabatic heating and tropical cyclone intensification: Efficiency of Diabatic Heating in Tropical Cyclones
Smith, Roger K.
Montgomery, Michael T.
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Widely held arguments attributing the increasingly rapid intensification of tropical cyclones to the increasing ‘efficiency’ of diabatic heating in the cyclone’s inner core region associated with deep convection are examined. The efficiency, in essence the amount of temperature warming compared with the amount of latent heat released, is argued to increase as the vortex strengthens on account of the strengthening inertial stability. Another aspect of the efficiency ideas concerns the location of the heating in relation to the radius of maximum tangential wind speed, with heating inside this radius seen to be more efficient in rapidly developing a warm-core thermal structure and, presumably, a rapid increase in the tangential wind. A more direct interpretation of the increased spin-up rate is offered when the diabatic heating is located inside the radius of maximum tangential wind speed. Further, we draw attention to the limitations of assuming a fixed diabatic heating rate as the vortex intensifies and offer reasons, on these grounds alone, as to why it is questionable to apply the efficiency argument to interpret the results of observations or numerical model simulations of tropical cyclones. Moreover, since the spin-up of the maximum tangential winds in a tropical cyclone takes place in the boundary layer and the spin-up of the eyewall is a result of the vertical advection of high angular momentum from the boundary layer, it is questionable also whether deductions about efficiency in theories that neglect the boundary-layer dynamics and thermodynamics are relevant to reality.
The article of record as published may be found at https://doi.org/10.1002/qj.2804
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