Geoscience Reference
In-Depth Information
Fig. 10. EDR maps (a) at 21:32 UTC on 27 April 2006 and (b) 13:17 UTC on 13 June 2008. The
mountainous Lantau Island is located to the south of the radar scans.
Another issue of the comparison is the contribution of mean wind shear to the measured
spectrum width. For the estimation of EDR, the contribution of wind shear has to be
extracted from the radar measured spectrum width. But for the comparison with aircraft
measured EDR or even turbulence alert for aviation safety, wind shear might not need to be
removed. For example if the aircraft experiences a sharp change in altitude, this may not be
caused by isotropic turbulence but it is a measure of aircraft response to vertical shear of
mean wind. As such, the aircraft estimated EDR based on vertical velocity may be slightly
higher. Pilots and passengers in aircraft may also experience severe “turbulence”, which is a
combination of the effects of both turbulence and wind shear.
Scatterplots of median and maximum EDR along the 5 nm of flight paths estimated by
aircraft and radar are shown in Figure 11. Two plots for each are shown; one in which mean
wind shear contributions to the observed spectrum widths are removed and a second plot in
