Parameterizing Sea Surface Temperature Cooling Induced by Tropical Cyclones

Sea surface temperature cooling (SSTC) induced by tropical cyclones (TCs) could produce a significant impact on the storm intensity. Although a coupled atmosphere-ocean model provides such SSTC by design, various challenges associated with coupled modeling often lead many TC researchers to continue to use atmosphere-only models. Therefore, the main goal of this study is to develop a fast, robust, and effective parameterization scheme for TC-induced SSTC that can be used in atmosphere-only TC prediction models. The following three steps are taken to achieve this goal: (i) results from an idealized ocean simulation, together with theoretical and temperature budget analyses, are analyzed to isolate each major mechanism causing TC-induced SSTC, which is then used as a basis for the parameterization; (ii) building upon the idealized ocean simulation, the new SSTC parameterization scheme includes vertical mixing, advection, and SST recovery processes under the influence of sea surface height and ocean subsurface temperature; and (iii) this TC-induced SST scheme is incorporated into the Weather Research and Forecasting model, from which numerical simulations of Typhoon Matsa (2005) are run and then validated against various remote sensing and in situ data. Results from this proof-of-concept demonstration show significant improvements in the simulated storm intensity and reasonable SST changes after applying this parameterization scheme. Although further testing with more TC cases is needed, these results are promising, and the parameterization scheme should be compatible with any TC weather prediction model. This scheme can also produce realistic distributions of TC-induced ocean surface circulations in relation to SSTC during and after TC passage.