Dependence of tropical-cyclone intensification on the boundary-layer representation in a numerical model

We present idealized numerical model experiments to investigate the dependence of tropical-cyclone intensification and, in particular, the kinematic structure of the tropical-cyclone boundary layer on the boundary-layer parametrization in the model. The study is motivated by recent findings highlighting the important dynamical role of the boundary layer in tropical-cyclone intensification. The calculations are carried out using the Pennsylvania State University– National Center for Atmospheric Research fifth-generation mesoscale model (MM5). Predictions using one of five available schemes are compared, not only between themselves, but where possible with recent observational analyses of boundary-layer structure. At this stage the study falls short of being able to advocate the use of a particular scheme, although certain shortcomings of individual schemes are identified. The current inability to determine ‘the optimum scheme’ has implications for the predictability of tropical-cyclone intensification.