Tropical cyclone intensification: Sensitivity to the boundary-layer parameterization in a numerical model

The important dynamical role of the boundary layer to tropical-cyclone intensification has been highlighted in Part I. This talk addresses the sensitivity of the intensification process to different boundary-layer parameterizations in a numerical model. Using the three-dimensional, non-hydrostatic models MM5 and WRF, we compare the bulk-aerodynamic, Blackadar, Burk-Thompson, MRF, Gayno-Seaman and YSU schemes in an idealized model configuration. The results indicate that the different properties of these schemes have a significant influence on the details of the vortex intensification process including the time of rapid intensification, the mature intensity and the vortex 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.