89th American Meteorological Society Annual Meeting

Monday, 12 January 2009: 2:15 PM
Evaluation of high resolution forecasts of microwave refractivity in a coastal environment
Room 126A (Phoenix Convention Center)
William T. Thompson, NRL, Monterey, CA; and T. Haack
A high-resolution mesoscale model with sophisticated data assimilation, SST analysis, surface and boundary layer parameterization schemes is used to diagnose evolving microwave refractivity structures in topographically complex coastal settings. These structures can lead to ducting of microwave energy which has direct implications for the operation of radar systems. In this study, we analyze the performance of the high resolution model using data from a series of measurements of microwave propagation and meteorological fields carried out in the vicinity of Wallops Island, VA in April and May 2000. Model output is used to diagnose the modified refractivity yielding ducting structures, including horizontal distribution and frequency as well as thickness, strength, duct base height, and percentage of surface-based ducts.

Evaluation of 7-days of intensive observations with 4-km resolution model fields permits characterization of ducting patterns influenced by diurnal, mesoscale and synoptic forcing and to establish model deficiencies and limitations. Further, the model-predicted modified refractivity provides environmental input to propagation models that describe radar system performance based upon atmospheric effects. The results from the Naval Research Laboratory's model COAMPS are being analyzed along with those of five other models in an inter-comparison study to determine the impact of model errors on radar propagation and define key areas of model improvement. A comprehensive model validation and verification statistics will be shown at the meeting.

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