The 8th Conference on Aviation, Range, and Aerospace Meteorology

P13.4
ACCURACY OF RUC-1 AND RUC-2 WIND AND AIRCRAFT TRAJECTORY FORECASTS AS DETERMINED BY ACARS OBSERVATIONS

Stanley G. Benjamin, NOAA/FSL, Boulder, CO; and B. E. Schwartz

The Rapid Update Cycle, a high-frequency short-range analysis forecast system in the USA, is designed, in part, to be a source of wind data for use by air traffic management over the United States. According to recent studies by NASA Ames, despite the relative accuracy of the RUC information, wind errors are still the primary contributor to trajectory errors. A new assessment of wind forecast accuracy for air traffic management is presented here, including improvements from the new 40-km 40-level version of the RUC, including a 1-h update cycle, implemented in April 1998 at NCEP.

In this study, wind forecast errors in the Denver terminal airspace (covering approximately 1,800,000 sq km) were determined and analyzed over a 13-month period from Aug 1996 -- Aug 1997 using almost 1,800,000 ACARS wind observations. This study showed that the 40-km RUC improved short-range forecast RMS vector errors by about 0.5-0.7 m/s. Because the new 40km RUC also runs on a 1-h cycle, air traffic management can be performed with 1-2 h forecasts, as opposed to the 3-5 h forecasts used with the previous 60-km RUC running on a 3-h cycle. The difference in RMS vector error between 1-2h forecasts from the 40km RUC and 3-5h forecasts from the 60km RUC is quite substantial, about 1.2 m/s.

Direct calculations have been made of aircraft trajectory times (about 20 minutes long) from ACARS observations themselves, and also from RUC-2 forecasts. These results will also be presented, along with a study of wind forecast errors by time of day, altitude, geographic sector, and type of weather

The 8th Conference on Aviation, Range, and Aerospace Meteorology