On the role of radiation in tropical cyclone dynamics

A common assumption in theoretical studies of tropical cyclone dynamics involves ignoring or severely approximating the role of electromagnetic radiation. For example, in theories for steady-state storm intensity, radiation plays no role except as an implicit upper boundary condition that conveys entropy drawn from the sea surface to space. Similarly,idealized modeling experiments of tropical cyclone dynamics often employs Newtonian cooling in order to balance warming due to latent heat release. Justification for such approximations include thermodynamic scale analysis, and previous numerical studies showing equivocal impact of radiation on tropical cyclone development. Scale analysis suggests that the surface flux of entropy near the eyewall is large relative to the local radiative change in entropy, and previous studies suggest that, relative to Newtonian cooling, the main role of radiation is to increase the development rate of storms by cooling the atmosphere outside the eyewall. Assumed cooling rates affect not only intensification rates, but also storm structure, which has received little attention. The impact of radiation on both steady-state storm intensity and structure will be discussed and diagnosed from numerical simulations. We show that assumed cooling rates adversely affect steady-state storm structure, and nearly eliminate temporal variability relative to solutions including infrared radiation.