Extended Abstract (36K)17C.4
A minimal hurricane model with a coupled mixed layer ocean
Wolfgang Ulrich, Univ. of Munich, Munich, Germany
The minimal 3-layer hurricane model of Zsu et al. (2001) has been coupled to a simple model of the ocean's mixed layer to provide a minimal coupled hurricane-ocean model research. The model is being used to explore the sensitivity of hurricane intensification to ocean feedback. In the basic calculation, a weak vortex is initiated on a beta-plane in an environment at rest. There is positive feedback in the initial development stage of the vortex: as the vortex intensifies, so does the surface flux of latent heat. Later there is a negative feedback caused by upwelling of cold water, driven by surface drag, which lowers the SST from the mature stage onwards. We show that the strength of the negative feedback depends not only on the initial states of the atmosphere and the ocean, but also a significant degree on the physical parameterizations used in both the hurricane model and the ocean model. The details of the coupling have far reaching consequences for the ocean mixed layer and for the SST.
The type of the mixing parameterization that determines how thermocline water is brought into the mixed layer induces either a larger region of only slightly reduced SST or a more localized region of considerable lowered SST, which in turn leads to profound differences in the deep convection coverage, depending on which type of convection scheme is used in the minimal hurricane model.
Session 17C, Tropical Cyclone Air-Sea Interaction IV (Parallel with Sessions 17A and 17B)
Friday, 3 May 2002, 11:00 AM-12:30 PM
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