Geoscience Reference
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turbulence only occurs at one radar gate at the distance of 0 nm, closest to the end of the
runway. It is noted that at this location, the radar beam is higher than the flight path by
about 160m.
We have also compared aircraft and radar estimated EDR profiles including wind shear
contribution along the aircraft flight path. For this case, aircraft B777 flew through a storm
with maximum reflectivity of 42 dBZ and landed in clouds and light rain at HKIA.
Figure 12 shows the EDR estimated by aircraft and the radar along the flight path 25RA
around 13:05 UTC on 19 April 2008. It is one of the two cases in which severe turbulence
was encountered by the aircraft. Blue dots in Figure 13 represent the EDR estimated by the
aircraft as it was landing at HKIA. Three peaks over 0.5
2/3
ms
, classified as severe
turbulence, are recorded at distance of 0.77, 3.65, and 4.90 nm away from the runway end.
EDR profiles estimated by using radar data at an elevation angle of 0.6
o
with the wind shear
contribution included in the volume scans around 13:05 UTC are overlaid onto the aircraft
estimated EDR in Figure 13. The radar estimated EDR profiles at 13:01, 13:05, and 13:09 UTC
(brown dots, red squares, and green dots in Figure 13) matches well with aircraft EDR
between distance of 0.5 and 1.5 nm, shaded in green color in Figure 13, where the aircraft
was in a region common to the 0.6
o
radar beam. It means that radar and aircraft were
measuring turbulence in approximately the same region at nearly the same time.
Fig. 12. (a) EDR, (b) spectrum width, (c) reflectivity factor, and (d) Doppler velocity at
elevation angle of 0.6
o
at 13:05 UTC on 19 April 2008. Range ring is at 10 km.
The peaks of these 3 EDR profiles at 13:01, 13:05, and 13:09 UTC are in the green shaded
interval and the maximum value is 0.48
2/3
ms
, just slightly smaller than 0.5
2/3
ms
. In
order to find if there are higher EDR near the flight time (13:05 UTC), we examined the EDR
for the two scans one minute before and after the passage of the aircraft at 13:05 UTC in the
same volume scan at 13:05 UTC. The profiles are shown with light and dark purple dots in
Figure 13. High EDRs with values of 0.69 and 0.76
2/3
ms
are found within the shaded
