LIDAR Observations of Terrain-induced Flow and Its Application in Airport Wind Shear Monitoring

19-23 May 2003

LIDAR Observations of LIDAR Observations of Terrain-induced Flow and Its Terrain-induced Flow and Its Application in Airport Wind Application in Airport Wind Shear MonitoringShear MonitoringCM Shun, CM Cheng & O LeeCM Shun, CM Cheng & O LeeICAM/MAP 2003ICAM/MAP 2003

19-23 May 2003

BackgroundBackground

Weather Buoys

Automatic WeatherStations over Lantau

TDWR

Weather buoy (3)

(1+2)

Sham Wat (2)

Wind Shear: terrain disrupted flow; thunderstorms; sea breeze

19-23 May 2003

LILIght ght DDetection etection AAnd nd RRanging (anging (LIDARLIDAR) System) System

LIDAR Scanner

ATC Building Roof-top

Installed in mid-2002

IR (2 μm) → eye-safe

19-23 May 2003

LIDAR in Tropical CycloneLIDAR in Tropical Cyclone

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Jump Like Feature (11 Nov Jump Like Feature (11 Nov 2002)2002)

465 m

stagnant flow

jump

Lo Fu Tau

N = 0.0135 s-1

h = 465 mU0 ~ 5 ms-1

Nh/U0 ~ 1.3 > 0.85 (wave breaking)Weak inversion (0.4ºC) below 500 m

Inversion near 3 km

100º

19-23 May 2003

Jump Like Feature (20 Jan Jump Like Feature (20 Jan 2003)2003)

reverseflow

reverse flow

jump

Lo Fu Tau

N = 0.013 s-1 h = 465 m U0 ~ 6 ms-1

Nh/U0 ~ 1.0 > 0.85 (wave breaking)Inversion: 1.1&1.5ºC 500-700 m = 3.6 K = 291 K D ~ 600 m Fr = U0 / (g’D)½ ~ 0.7M = h/D ~ 0.8Schär & Smith (1993) Regime IIb

Inversion at 500-700 m

095º

19-23 May 2003

Jump StructureJump Structure22-min Sequence (@ 2 min)22-min Sequence (@ 2 min)

095º

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Vortex SheddingVortex Shedding12-minute Sequence (@ 2 min)12-minute Sequence (@ 2 min)

100º

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Springtime Wind ShearSpringtime Wind Shear(5 March 2003)(5 March 2003)

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Temperature JumpTemperature Jump

Buoy (north)

Buoy (south)

+4ºC

+5ºC

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Buoy (north)

Buoy (south)

Land Station (SW1)

Wind Changes (Wind Changes (EESS))

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Descent of Warm JetsDescent of Warm Jets

297 K

2025°C

20°C

19°C

00 UTC 0317 UTC

N = 0.02 s-1

h = 934 m (Lantau Peak)U0 19 ms-1

Nh/U0 1 (descending flow / hydraulic jump)

1. How to apply Fr under strong vertical shear?

2. Contribution of gap-flow?3. Interaction between jets?

19-23 May 2003

Time - Azimuth Plot of Time - Azimuth Plot of LIDAR radial velocityLIDAR radial velocity

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ConclusionsConclusions

Jump-like features & vortex shedding under Jump-like features & vortex shedding under stable conditions are revealedstable conditions are revealed

Nh/UNh/U00 & Fr able to diagnose jump based on & Fr able to diagnose jump based on Schär & Smith (1993)

Springtime wind shear - interaction of Springtime wind shear - interaction of descending S’ly jet (also a jump?) with surface descending S’ly jet (also a jump?) with surface E’ly jetE’ly jet

More work is needed to better understand More work is needed to better understand phenomena (Nh/Uphenomena (Nh/U00 & Fr in strong vertical shear; & Fr in strong vertical shear; gap-flow dynamics) gap-flow dynamics)

19-23 May 2003

Thank You!