7.2 Identifying upper-level wake vortex encounters using routine turbulence reports

Wednesday, 9 January 2013: 8:45 AM
Room 17A (Austin Convention Center)
John K. Williams, NCAR, Boulder, Colorado; and G. Blackburn, J. A. Craig, R. K. Goodrich, J. Johnson, F. McDonough, G. Meymaris, J. M. Pearson, and R. D. Sharman

This paper presents results of a study to determine whether aircraft encounters with wake vortices generated by preceding aircraft in the upper troposphere and lower stratosphere are evident in routine reports of moderate or severe turbulence. Based on case-study analyses, an aircraft wake encounter simulation and statistical analysis of pilot reports and automated in situ eddy dissipation rate (EDR) reports from in-service commercial aircraft, the authors demonstrate that some turbulence reports are caused by wake vortex encounters. For example, a statistical analysis of one year of Aircraft Situation Display to Industry data, Enhanced Traffic Management System data, and in situ EDR data from about 100 Delta Air Lines aircraft identified 44 suspected wake vortex encounters.

These results have several implications:

1) Aircraft encounters with wake vortices outside the terminal area may pose a more significant safety risk than has been previously recognized.

2) The safety risk may increase under NextGen, which prescribes reduced aircraft separations.

3) Turbulence reports currently used for verification and tuning of turbulence forecast products are contaminated by wake vortex encounters.

4) The authors' method could be used to produce a database with precise locations and times of a large number of wake vortex encounters. This database could support a study characterizing the atmospheric conditions and aircraft proximities most likely to lead to significant wake encounters, potentially facilitating development of effective mitigation strategies or a system for predicting wake encounter risk based on numerical weather prediction model forecasts.

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