A Modeling Study of Typhoon Toraji (2001): Physical Parameterization Sensitivity and Topographic Effect

桃芝(2001)颱風之模擬研究：物理參數法敏感度及地形效應

楊明仁(Ming-Jen Yang) ； 青麟(Lin Ching)

《Terrestrial, Atmospheric and Oceanic Sciences》 16卷1期 (2005/03) Pp. 177-213

並列摘要

This paper investigates the dependence of simulated track, central pressure, maximum wind, and accumulated rainfall of Typhoon Toraji (2001) on physical parameterizations, using the fifth-generation Pennsylvania State University- National Center for Atmospheric Research Mesoscale Model (MM5). The model configuration includes three nested domains with grid size of 60,20, and 6.67 km, respectively. Three sets of five numerical experiments on cumulus, cloud microphysics, and planetary boundary layer (PBL) parameterizations are performed (15 experiments totally). Among subgrid-scale cumulus schemes tested, the simulated typhoon with the Grell scheme has the best track. For grid-scale cloud microphysics scheme examined, all storms have similar tracks, with the best simulated track using the Goddard Graupel cloud microphysics scheme. The PBL parameterization substantially affects the simulated typhoon tracks, and the storm with the Medium-Range Forecast model PBL has track and intensity that most resemble actual observations.
An experiment with the best scheme from each of three sets of physical parameterization experiments has the best performance in terms of central pressure, maximum wind and accumulated rainfall; it can simulate the westward turning of Toraji's track right before the landfall. Standard deviation and ensemble (arithmetic) mean are calculated for each set of physical parameterization experiments. The ensemble-mean track and rainfall distribution are much closer to the observations than each individual experiment. A combination of the topographically- and environmentally-induced vertical moisture fluxes, calculated based on the flux model of Lin et al. (2001), corresponded well to the hourly surface rainfall distribution. An analysis of nondimensional parameters for typhoon's track continuity over the Taiwan island shows that Typhoon Toraji's track discontinuity is consistent with the control parameter analysis proposed by Lin et al. (2002). The westward turning of Toraji's track right before the landfall may be caused by horizontal advection process due to flow blocking, on the basis on a momentum budget analysis.

並列關鍵字

Typhoon ； Physical parameterization ； Topographic effect ； Toraji ； MM5