1. 19-23 May 2003 LIDAR Observations of Terrain- induced Flow and Its Application in Airport Wind Shear Monitoring CM Shun, CM Cheng & O Lee ICAM/MAP 2003

2. 19-23 May 2003 Background Weather Buoys Automatic Weather Stations over Lantau TDWR Weather buoy (3) (1+2) Sham Wat (2) Wind Shear: terrain disrupted flow; thunderstorms; sea breeze

3. 19-23 May 2003 LIght Detection And Ranging (LIDAR) System LIDAR Scanner ATC Building Roof-top Installed in mid-2002 IR (2 μ m) → eye-safe

4. 19-23 May 2003 LIDAR in Tropical Cyclone

5. 19-23 May 2003 Jump Like Feature (11 Nov 2002) 465 m stagnant flow jump Lo Fu Tau N = 0.0135 s -1 h = 465 m U 0 ~ 5 ms -1 Nh/U 0 ~ 1.3 > 0.85 (wave breaking) Weak inversion (0.4ºC) below 500 m Inversion near 3 km 100º

6. 19-23 May 2003 Jump Like Feature (20 Jan 2003) reverse flow reverse flow jump Lo Fu Tau N = 0.013 s -1 h = 465 m U 0 ~ 6 ms -1 Nh/U 0 ~ 1.0 > 0.85 (wave breaking) Inversion: 1.1&1.5ºC 500-700 m  = 3.6 K  = 291 K D ~ 600 m Fr = U 0 / (g’D) ½ ~ 0.7 M = h/D ~ 0.8 Schär & Smith (1993) Regime IIb Inversion at 500-700 m 095º

7. 19-23 May 2003 Jump Structure 22-min Sequence (@ 2 min) 095º

8. 19-23 May 2003 Vortex Shedding 12-minute Sequence (@ 2 min) 100º

9. 19-23 May 2003 Springtime Wind Shear (5 March 2003)

10. 19-23 May 2003 Temperature Jump Buoy (north) Buoy (south) +4ºC +5ºC

11. 19-23 May 2003 Buoy (north) Buoy (south) Land Station (SW1) Wind Changes (E  S)

12. 19-23 May 2003 Descent of Warm Jets 297 K 20  25°C 20°C 19°C 00 UTC 0317 UTC N = 0.02 s -1 h = 934 m (Lantau Peak) U 0  19 ms -1 Nh/U 0  1 (descending flow / hydraulic jump) 1.How to apply Fr under strong vertical shear? 2.Contribution of gap-flow? 3.Interaction between jets?

13. 19-23 May 2003 Time - Azimuth Plot of LIDAR radial velocity

14. 19-23 May 2003 Conclusions Jump-like features & vortex shedding under stable conditions are revealed Jump-like features & vortex shedding under stable conditions are revealed Nh/U 0 & Fr able to diagnose jump based on Nh/U 0 & Fr able to diagnose jump based on Schär & Smith (1993) Springtime wind shear - interaction of descending S’ly jet (also a jump?) with surface E’ly jet Springtime wind shear - interaction of descending S’ly jet (also a jump?) with surface E’ly jet More work is needed to better understand phenomena (Nh/U 0 & Fr in strong vertical shear; gap-flow dynamics) More work is needed to better understand phenomena (Nh/U 0 & Fr in strong vertical shear; gap-flow dynamics)

15. 19-23 May 2003 Thank You!