On the role of surface friction in tropical cyclogenesis

Through a series of numerical experiments using MM5 the role of surface friction in tropical cyclogenesis is studied. The results do not support the concept of dual role of surface friction as proposed by Charney and Eliassen in their CISK theory. Surface friction plays in tropical cyclogenesis only its conventional role—damping. The concept that friction can induce convergence in the boundary layer and thus plays an instability-enhancing role is not supported by the experimental results.