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SHEN Xinyong, LIU Jia, QIN Nannan, FENG Jin. 2013: Impact of Viscous Friction on Barotropic Eigenvalue Wave of Typhoon Matsa after Its Landing. Chinese Journal of Atmospheric Sciences, 37(6): 1219-1234. DOI: 10.3878/j.issn.1006-9895.2013.12047
Citation: SHEN Xinyong, LIU Jia, QIN Nannan, FENG Jin. 2013: Impact of Viscous Friction on Barotropic Eigenvalue Wave of Typhoon Matsa after Its Landing. Chinese Journal of Atmospheric Sciences, 37(6): 1219-1234. DOI: 10.3878/j.issn.1006-9895.2013.12047

Impact of Viscous Friction on Barotropic Eigenvalue Wave of Typhoon Matsa after Its Landing

  • In this study, barotropic equations including a friction term are derived in cylindrical coordinates. The numerical differential method is applied to the barotropic equations to construct the characteristic wave solutions. The data from a Weather Research and Forecasting model simulation of typhoon Matsa at 1500 LST on August 6, 2005 are then used to calculate the barotropic characteristic wave structures to study how they are affected by friction inside typhoon Matsa. The results show that the wavenumber is 45 for most unstable external inertia-gravity waves, which are weakened by friction. The waves propagate counterclockwise, and the wave speed for wavenumber 1 at a radius of 1000 km is 47.43 m/s. Perturbed radial winds increase and convergence strengthens at radii greater than 800 km. The wavenumber is 2 for most unstable vortex Rossby waves, whose growth rate is reduced by friction. The wave speed is 4.282-29.172 m/s at a radius of 200 km; the area of large perturbed vorticity decreases, and the area of the vortex Rossby waves shrinks toward the typhoon's center. When all the waves are considered, friction weakens the waves at wavenumber 45. The wave speed of wavenumber 1 is 26.374 m/s at a radius of 1000 km, whereas it is 5.275 m/s at a radius of 200 km. The wave speed of wavenumber 1 becomes 30.324 m/s at a radius of 1000 km and 6.065 m/s at a radius of 200 km when the radial wind is considered. The friction significantly increases the perturbed radial winds and enhances the convergence.
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