Geoscience Reference
In-Depth Information
NHMFST 2010/07/28 03.00Z FT = 2:00
850
VOR
850
STRM
NHMFST 2010/07/28 03.00Z FT= 2:00
850
VOR
850
STRM
CNTL
VOR
STRM
CNT=
(KNOT)
50.00
MAX=
MAX=
1508.89
36.70
MIN=
MIN=
−
723.78
8.57
VALID= 07/28
13:00HKT
VOR
STRM
CNT=
(KNOT)
50.00
MAX=
MAX=
1280.88
38.46
MIN=
MIN=
−
688.91
6.42
VALID= 07/28
13:00HKT
−
750
−
500
−
250
0
250
500
750
−
750
−
500
−
250
0
250
500
750
Fig. 22.7
h forecast relative vorticity on 850 hPa level (positive/cyclonic vorticity in
red
and vice versa for
blue
) using radar retrieval winds (
left
)andCNTL
T
C
2
both experiments are based on 1 h forecast of corresponding 0300 UTC run. It
is found that radar retrieval winds and Doppler velocity data corresponding to
convection over the coastal waters (Area C in Fig.
22.3
) are assimilated in RAPIDS-
NHM to generate disturbances in the southwesterly flow and enhanced the cyclonic
vorticity (Fig.
22.9
). A north-south oriented reflectivity band is thus be forecast
through the use of radar retrieval data (Fig.
22.10
), although the timing for the
arrival and merging of two echo bands over HK remain lagged behind by about 1 h.
Figure
22.11
shows 3-h accumulated rainfall forecasts ending at 0830 UTC (1630
HKT) from the two experiments. With radar retrieval winds in the initial condition,
rainfall generally over Hong Kong and Lantau Island is forecast to exceed 100 mm
in3hthatissimilartotheactualcondition. In RAPIDS-NHM forecast, the merging
of rainband and hence the maximum rainfall areas are found over southeastern part
of territory, while in actual they are located mainly to the east of Hong Kong.
22.4
Application of LIDAR Data and Wind Retrieval Using
Variational Techniques
22.4.1
Doppler LIDAR for Windshear Alerting in Hong Kong
International Airport
For the alerting of low-level windshear and turbulence in clear air, non-rainy
weather conditions, two Doppler
LI
ght
D
etection
A
nd
R
anging (LIDAR) systems
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