Revisiting dissipative heating in tropical cyclone maximum potential intensity

In this study, we re-examine the hypothesis of the dissipative heating in the tropical cyclone (TC) maximum potential intensity (MPI) proposed by Bister and Emanuel in 1998. By analysing an integral energy equation for an atmospheric domain that encloses all the TC Carnot legs, it is shown that the dissipative heating within the boundary layer is inherently contained in the energy budget so that there is no need to treat it separately. Due to the well-mixed assumption, the net impact of the dissipative heating turns out to be negligible, resulting in the same MPI estimation as in Emanuel's 1986 article. Within the atmospheric surface layer, the dissipative heating comes at the expense of reduced internal kinetic energy in the boundary layer, which is not seen in Bister and Emanuel's formulation due to their assumption of constant wind speed within the atmospheric surface layer. Analysis of the energy distribution within the atmospheric surface layer shows that about 10-30% of the frictional work could be transferred to the ocean surface waves and oceanic well-mixed layer, and the assumption that all frictional work is converted to the dissipative heating therefore needs to be revisited. Given further uncertainties in how the dissipative heating is distributed within the surface layer and how the atmospheric surface layer exchanges heat with the ambient environment, we recommend use of the original MPI formula obtained by Emanuel (1986) in which the impact of the dissipative heating within the surface layer can be effectively included in the bulk enthalpy flux parametrization instead of considering dissipative heating as an independent heat source as proposed by Bister and Emanuel.