Extended Abstract (360K)P1.33
Role of tropical cyclones in large-scale momentum, heat, and moisture budgets
Andrew S. Levine, University of Hawaii, Honolulu, HI; and K. P. Hamilton
Standard calculations of eddy contributions to the zonal mean heat, moisture and momentum budgets use global meteorological analyses that poorly represent tropical cyclones. These calculations may greatly underestimate any storm-related eddy transports. Can the contributions from tropical cyclones to eddy transports be ignored? If the storms are important in the global heat, moisture, and momentum budgets, then it will be necessary to adequately represent their effect (by parameterization) in modest-resolution global models that can be applied to climate sensitivity problems. Here we will attempt to characterize the eddy transports associated with tropical cyclones in a fairly short control integration with an ultra-fine resolution global atmospheric general circulation model (GCM).
The GFDL "SKYHI" GCM has been integrated with a horizontal resolution of 0.33 degrees (N270) and also fine vertical resolution (40 levels). In a single simulated Northern Hemisphere tropical cyclone season, this model produced at least 30 identifiable tropical cyclones, including some very intense ones (Hamilton and Hemler, 1997). Output for the month of July is the focus of this study. There were seven typhoons in the model output for this month, including two super typhoons. A spatial smoothing function is applied to the SKYHI output to degrade the resolution from N270 to N25 (3.6 degrees), which largely removes the signature of tropical cyclones. Eddy transports are calculated from the full model output using 12 hour snapshots, and are compared with transports computed with the smoothed output. When the smoothing is applied over the full data set, the computed eddy transports in the band from 5N-35N are generally reduced by ~10%. These calculations are being extended to employ a processing that smoothes only in the vicinity of intense typhoons. This will allow the contributions to eddy transports from the typhoons to be isolated. Preliminary results indicate the influence of tropical cyclones on global heat, moisture, and momentum budgets may be significant.
Poster Session 1, Posters
Wednesday, 5 May 2004, 1:30 PM-1:30 PM, Richelieu Room
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