Validation of SODAR real-time sensing and visualisation of wake vortices

Acoustic wind and turbulence profilers (SODARs) have proven to be particularly effective, across many applications, in real-time observation of the lowest few hundered meters in the atmosphere. This is largely because of operational reliability in virtually all weather conditions. We report on continuous real-time operational monitoring of wake vortices using an array of SODARs at a major US airport. Each vertical wind speed profile, comprises a matrix of wind speeds at each height range (determined by acoustic pulse characterisitics), and each horizontal position (determined by SODAR spacing). These 'snap-shots', every 2 seconds, are individually analysed so as to estimate best values of vortex circulation and position. This is achieved using least-squares fitting, of the data matrix against a simple vortex model, which also returns reliability of the vortex strength and position estimates. The resulting time-sequence of vortex development is then presented in a number of ways as a real-time visualisation. Important features of this work are: use of a proven technology; validation at vortex generation against known aircraft characteristics (before substantive vortex-meteorological interaction); use of very simple assumptions in the parameter-extraction model so that the estimated parameters are not constrained; and real-time processing and display, with reliability estimates, in a wide range of atmospheric conditions.