P2D.10 Do gravity waves transport angular momentum away from tropical cyclones?

Thursday, 1 May 2008
Palms ABCD (Wyndham Orlando Resort)
Yumin Moon, University of Miami, Miami, FL; and D. S. Nolan

Latent heating within convective clouds in and around a tropical cyclone creates a localized departure from hydrostatic and gradient wind balance. In response, hydrostatic and geostrophic adjustment processes gradually establish a new equilibrium in the atmosphere by dispersing the source of imbalance to the surrounding through gravity waves. To accurately compute the effect of convection on tropical cyclones, it is critical to capture these rapid adjustment processes.

Latent heat release within convection is the source of energy that maintains the storm, and thus gravity waves are ubiquitous in tropical cyclones. Previous studies have suggested that gravity waves radiating from the core of a tropical cyclone can effectively transport a large amount of angular momentum away from the storm. This study uses a simple three-dimensional, nonhydrostatic, but linear model to clarify how efficient gravity waves are in removing angular momentum of the storm. This model is capable of representing the realistic three-dimensional structure of the storm and can capture the full three-dimensional adjustment processes. Calculations indicate that gravity waves do carry angular momentum away from the storm's inner-core region but at a significantly smaller rate, on the order of 0.1 % per day.

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