Wind and Temperature Verification Statistics for the Operational Terminal Area PBL Prediction System at the Dallas-Fort Worth International Airport

This paper will address the multi-month statistical accuracy of the Terminal Area PBL Prediction System (TAPPS). TAPPS is being run operationally in support of the Aircraft Vortex Spacing System (AVOSS) demonstration at the Dallas-Fort Worth (DFW) International Airport under the auspices of the NASA-Langley Research Center. AVOSS is an element of NASA's Terminal Area Productivity Program (TAP) that is designed to incorporate wake vortex observations, wake vortex decay and transport algorithms, the observed and predicted weather state, and system integration to determine the minimum safe spacing for departing and arriving aircraft in order to avoid unsafe encounters with aircraft wake vortices. A concept demonstration of the system is planned for Dallas-Ft. Worth (DFW) airport in 2000. The motivation behind the development of this system is the need for increased airport capacity while maintaining the present level of safety. Means of safely increasing airport capacity will be a critical issue as the number of flights to and from U.S. airports increases substantially in the near future.

The centerpiece of TAPPS is a mesoscale numerical weather prediction model that is run twice daily over a grid mesh centered on the DFW International Airport. TAPPS (version #1) is integrated over a matrix of 60X60X56 grid points and essentially represents Version 5.13 of the Mesoscale Atmospheric Simulation System (MASS). This mesoscale numerical weather prediction model employs the Blackadar PBL parameterization scheme, Kuo-MESO convective parameterization scheme, a comprehensive soil moisture hydrology and land use parameterization scheme, as well as very detailed vertical resolution within the lower part of the PBL. The highest resolution version of the model utilizes a 12 km horizontal fine grid mesh nested within a 24 km horizontal coarse grid mesh. The coarse grid mesh is initialized from NWS ETA analyses data sets and integrated for 24 hours of real-time on a DEC-ALPHA 600 workstation. The fine grid mesh is then integrated for 21 hours, starting 3 hours after the observation time, and using the coarse grid mesh results as lateral boundary conditions.

Routinely available products include 15 m vertical resolution soundings of the cross-runway wind component, along-runway wind component, virtual potential temperature, eddy dissipation rate, turbulent kinetic energy, and wind variance up to ~1005 m elevation. Also available are time-height sections of these same fields based on 30 minute interval simulated model results.

Observations from the DFW PBL profiler, RASS, and MIT Lincoln Laboratory AWAS profiles will be compared to the TAPPS #1 simulations for a multi-month time period. Error statistics, including the mean absolute error, RMS error, and bias of the wind velocity components and temperatures will be discussed in terms of their vertical structure as well as their sensitivity to model initialization time, to the diurnal cycle, and to different synoptic weather regimes. Comparisons will also be made against a smaller sample of verification statistics from the second generation of the operational TAPPS (version #2), which includes improved initial soil moisture, improved initial winds, and ~6 km horizontal resolution simulations.