Sensitivity of typhoon-induced gravity waves to cumulus parameterizations

Sensitivity of typhoon-induced gravity waves to cumulus parameterizations is examined using a mesoscale model (MM5). For this, Typhoon Rusa (2002) is simulated with four cumulus parameterizations (Kain-Fritsch, Grell, Anthes-Kuo, and Betts-Miller schemes) and the characteristics of typhoon-induced gravity waves are compared. The experiments show differences in rainband structure and vertical motion, resulting in different forcing spectra for zonal wavelength and period. As a result, induced stratospheric gravity waves are different in amplitude and spectral shape. However, the difference is not as large as that in the forcing spectrum, since a large portion of the waves generated by major forcing components is filtered out by the background wind, which is nearly the same in all the experiments. Instead, variation in zonal wavelength and period of forcing modifies the characteristics of stratospheric gravity waves by changing damping time scale in the nonfiltered region.