The role of momentum transfer in tropical cyclogenesis: Insights from a single-column model

The analytical solution shows that the production of barotropic vorticity by the vortex-scale circulation is crucial for surface cyclone formation, and cumulus friction plays a dual role. Cumulus friction can enhance the downward momentum transfer, but when the eddy diffusion is too strong, the vortex-scale circulation is too damped to produce a significant barotropic cyclone. Between these two extremes lies an optimal eddy diffusivity that maximizes the growth rate of the surface cyclone.

Finally, we add surface friction to the single-column model. Using scale analysis, we identify a critical vortex Rossby number above which surface friction becomes nonnegligible and significantly damps the development of the surface cyclone.