Impact of Mesoscale Satellite Wind Data on Numerical Model Simulations: A Case Study

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  • 1 Department of Meteorology, University of Wisconsin, Madison, WI 53706
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Abstract

Initialization of a comprehensive mesoscale numerical prediction model is investigated using actual low-level mesoscale satellite wind observations in a case study. Attention is focused on describing and understanding the impact of these data on the model simulation with basic dynamical variables as well as precipitation. Three 6-h forecast experiments are made with the Kreitzberg-Perkey mesoscale model with 35 km horizontal resolution. These provide information on the sensitivity of the results to the method of data insertion.

Results show that the mesoscale divergence and vorticity fields in the satellite wind information remain coherent and identifiable well into the forecast period. Examination of the fields for specific scale ranges obtained by an objective scale decomposition shows that both the small- and large-scale components for vorticity persist for the entire 6 h period, whereas the divergence patterns of the inserted data are dissipated by 0.5 and 3 h respectively for the small- and large-scale components. After 3 h the primary impact of the inserted data is to alter the amplitude of mesoscale features that develop in the control experiment particularly for the horizontal divergence field. The satellite data produce some noticeable changes in the precipitation forecast in the 1–3 h period. Variations in results due to using different insertion procedures are small compared to differences between all the insertion experiments and the control except for a rather large amplitude external gravity wave oscillation produced by a gradual insertion technique.

Abstract

Initialization of a comprehensive mesoscale numerical prediction model is investigated using actual low-level mesoscale satellite wind observations in a case study. Attention is focused on describing and understanding the impact of these data on the model simulation with basic dynamical variables as well as precipitation. Three 6-h forecast experiments are made with the Kreitzberg-Perkey mesoscale model with 35 km horizontal resolution. These provide information on the sensitivity of the results to the method of data insertion.

Results show that the mesoscale divergence and vorticity fields in the satellite wind information remain coherent and identifiable well into the forecast period. Examination of the fields for specific scale ranges obtained by an objective scale decomposition shows that both the small- and large-scale components for vorticity persist for the entire 6 h period, whereas the divergence patterns of the inserted data are dissipated by 0.5 and 3 h respectively for the small- and large-scale components. After 3 h the primary impact of the inserted data is to alter the amplitude of mesoscale features that develop in the control experiment particularly for the horizontal divergence field. The satellite data produce some noticeable changes in the precipitation forecast in the 1–3 h period. Variations in results due to using different insertion procedures are small compared to differences between all the insertion experiments and the control except for a rather large amplitude external gravity wave oscillation produced by a gradual insertion technique.

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