Extended Abstract (192K)P3.1
Using WRF-ARW Data to Forecast Turbulence at Small Scales
Jeffrey E. Passner, Army Research Laboratory, White Sands Missile Range, NM; and D. I. Knapp
The Army Research Laboratory has an interest in high spatial and temporal resolution weather products with an emphasis on products that assist warfighter decision aids and applications in battlefield environments. In order to study and investigate small-scale weather processes, the advanced research Weather Research and Forecasting model (WRF-ARW) was run with a triple nest of 18, 6, and 2 km grids over a 24-h period. One of the long-term intriguing model areas of study is clear-air turbulence due to the influence of turbulence on Army Aviation missions. This study investigates the WRF over the urban New Jersey mainly during the cold season. Using a combination of the Panofsky Index in the boundary layer and Turbulence Index (TI) above the boundary layer, a small sample of 75 pilot reports was compared to “YES/NO” turbulence forecasts over the 24-h forecast period. Results were very encouraging at both 18-km and 2-km, with a probability of detection over 0.70, although the testing was biased to days with a high probability of turbulence. However, it was also found on the 2-km grid that the forecasted intensity of turbulence was excessive in many cases. There was no evident term in the TI that seemed to cause the problem; however, in many of these cases one or two terms were an order of magnitude higher at 2-km than at 18-km. It makes sense that a parameter such as turbulence would need to be parameterized at smaller scales; thus, an effort was made to treat the TI in the same way that a cumulus parameterization is treated. This methodology will be discussed in the paper and a deeper investigation to the predicament involved with turbulence intensity will be addressed in greater detail.
Poster Session 3, Turbulence, Volcanic Ash, and Instrumentation Posters
Wednesday, 23 January 2008, 2:30 PM-4:00 PM, Exhibit Hall B
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