Comparison of wake-vortex parameters measured by pulsed and continuous-wave lidars

Field trials carried out at Tarbes airfield in the summer of 2002 offered the unique opportunity to compare the results of simultaneous wake-vortex measurements by the 2-mu m pulsed Doppler lidar from DLR, German Aerospace Research Center, and the 10-mu m continuous wave (cw) Doppler lidars from ONERA and QinetiQ. The discrepancies in vortex core position obtained from the data of the pulsed lidar and the cw lidars; are 9 m for the vertical and 13 m for the horizontal co-ordinates. The accuracies of the vortex circulation measurements with the DLR and ONERA lidars are almost the same and equal 13 m(2)/s. This accuracy and the long-range capability of the pulsed lidar allows precise measurements over long periods from the moment of wake generation to a progressed state of vortex decay. Moreover, the influence of different atmospheric turbulence conditions and aircraft configurations on the wake-vortex circulation can be analyzed. This has been demonstrated out of ground effect under conditions of weak to moderate levels of turbulence.