Navy Operational Global Atmospheric Prediction System (NOGAPS) Analysis and Forecast Characteristics of Extratropical Cyclolysis over the North Pacific Ocean.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Simulations with high resolution airsea coupled models and several case studies have lead to the hypothesis that friction parameterizations could have a profound affect on the accuracy of numerical analysis and prediction of decaying cyclones. In this study, analyzed and forecast characteristics of decaying cyclones over the North Pacific Ocean are related to the hypothesized importance of friction induced cyclone spin down. Many characteristics of cyclolysis, which include gale area size and decay rate, were found to vary according to the synoptic-scale conditions in which the cyclone exists. Furthermore, the hypothesized relationship between cyclolysis and frictionally forced spin down was not found to exist in the analyzed and forecast model data. This result might be expected since friction spin down is parameterized based on analyzed and forecast winds over synoptic space and time scales. Therefore, it is concluded that over these scales other factors, which may include energy transfers due to barotropic processes, contribute in a major way to cyclone decay as portrayed in a global-scale numerical model.