The paper demonstrates the potential of the Doppler lidar technique fo
r the investigation of aircraft wake vortices. During several extended
field experiments at the Frankfurt/Main Airport, the DLR laser Dopple
r anemometer has measured the vortex properties of a large variety of
landing aircraft. These data are used to increase the understanding of
the behavior of wake vortices with special emphasis on the horizontal
vortex transport in ground effect. In particular, the results of the
vortex transport considerations are the basis for air traffic control
to enhance the efficiency of closely spaced parallel runway systems wi
th respect to wake vortices.