Characterizing regimes of strong terrain-induced winds in the vicinity of the Hong Kong International Airport
Alexander Gohm, Lukas Umek, Victoria Fetz
Institute for Meteorology and Geophysics, University of Innsbruck
ICAM 2013, Kranjska Gora, Slovenia
03 June 2013 Introduction Goals and Methods Results Conclusions Appendix Hong Kong International Airport (HKIA)
Regimes of strong terrain-induced winds at HKIA 2/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Hong Kong International Airport (HKIA)
Regimes of strong terrain-induced winds at HKIA 3/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Hong Kong International Airport (HKIA)
Regimes of strong terrain-induced winds at HKIA 4/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Hong Kong International Airport (HKIA)
Regimes of strong terrain-induced winds at HKIA 5/78 Alexander Gohm I No systematic study that relates upstream conditions to various flow regimes
I Shallow water model (SWM) is an easy and suitable tool for such a systematic study
I SWM has been successfully used in the past for other regions (e.g., Grubiˇsi´cet al. 1995; Pan and Smith 1999; Gohm and Mayr 2004; Gohm et al. 2008)
I Requirement for the SWM: two layer structure
I Example: 08 March 2006 ⇒ Chan and Cheung (2009) observed jets and flow reversal
Introduction Goals and Methods Results Conclusions Appendix Introduction
I Various case studies on severe terrain-induced winds at HKIA (e.g., Clark et al. 1997; Shun et al. 2003; Chan 2009, 2011a, b, 2012)
Regimes of strong terrain-induced winds at HKIA 6/78 Alexander Gohm I Shallow water model (SWM) is an easy and suitable tool for such a systematic study
I SWM has been successfully used in the past for other regions (e.g., Grubiˇsi´cet al. 1995; Pan and Smith 1999; Gohm and Mayr 2004; Gohm et al. 2008)
I Requirement for the SWM: two layer structure
I Example: 08 March 2006 ⇒ Chan and Cheung (2009) observed jets and flow reversal
Introduction Goals and Methods Results Conclusions Appendix Introduction
I Various case studies on severe terrain-induced winds at HKIA (e.g., Clark et al. 1997; Shun et al. 2003; Chan 2009, 2011a, b, 2012)
I No systematic study that relates upstream conditions to various flow regimes
Regimes of strong terrain-induced winds at HKIA 7/78 Alexander Gohm I SWM has been successfully used in the past for other regions (e.g., Grubiˇsi´cet al. 1995; Pan and Smith 1999; Gohm and Mayr 2004; Gohm et al. 2008)
I Requirement for the SWM: two layer structure
I Example: 08 March 2006 ⇒ Chan and Cheung (2009) observed jets and flow reversal
Introduction Goals and Methods Results Conclusions Appendix Introduction
I Various case studies on severe terrain-induced winds at HKIA (e.g., Clark et al. 1997; Shun et al. 2003; Chan 2009, 2011a, b, 2012)
I No systematic study that relates upstream conditions to various flow regimes
I Shallow water model (SWM) is an easy and suitable tool for such a systematic study
Regimes of strong terrain-induced winds at HKIA 8/78 Alexander Gohm I Requirement for the SWM: two layer structure
I Example: 08 March 2006 ⇒ Chan and Cheung (2009) observed jets and flow reversal
Introduction Goals and Methods Results Conclusions Appendix Introduction
I Various case studies on severe terrain-induced winds at HKIA (e.g., Clark et al. 1997; Shun et al. 2003; Chan 2009, 2011a, b, 2012)
I No systematic study that relates upstream conditions to various flow regimes
I Shallow water model (SWM) is an easy and suitable tool for such a systematic study
I SWM has been successfully used in the past for other regions (e.g., Grubiˇsi´cet al. 1995; Pan and Smith 1999; Gohm and Mayr 2004; Gohm et al. 2008)
Regimes of strong terrain-induced winds at HKIA 9/78 Alexander Gohm I Example: 08 March 2006 ⇒ Chan and Cheung (2009) observed jets and flow reversal
Introduction Goals and Methods Results Conclusions Appendix Introduction
I Various case studies on severe terrain-induced winds at HKIA (e.g., Clark et al. 1997; Shun et al. 2003; Chan 2009, 2011a, b, 2012)
I No systematic study that relates upstream conditions to various flow regimes
I Shallow water model (SWM) is an easy and suitable tool for such a systematic study
I SWM has been successfully used in the past for other regions (e.g., Grubiˇsi´cet al. 1995; Pan and Smith 1999; Gohm and Mayr 2004; Gohm et al. 2008)
I Requirement for the SWM: two layer structure
Regimes of strong terrain-induced winds at HKIA 10/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Introduction
I Various case studies on severe terrain-induced winds at HKIA (e.g., Clark et al. 1997; Shun et al. 2003; Chan 2009, 2011a, b, 2012)
I No systematic study that relates upstream conditions to various flow regimes
I Shallow water model (SWM) is an easy and suitable tool for such a systematic study
I SWM has been successfully used in the past for other regions (e.g., Grubiˇsi´cet al. 1995; Pan and Smith 1999; Gohm and Mayr 2004; Gohm et al. 2008)
I Requirement for the SWM: two layer structure
I Example: 08 March 2006 ⇒ Chan and Cheung (2009) observed jets and flow reversal
Regimes of strong terrain-induced winds at HKIA 11/78 Alexander Gohm Upstream conditions
I Layer height H0 = 520 m −1 I Wind speed U0 = 9 m s 0 ∆θ −2 I Reduced gravity g = g = 0.2 m s θ0 √ 0 I Froude number F0 = U0/ g H0 = 0.9
Introduction Goals and Methods Results Conclusions Appendix Introduction Radiosonde profile at Kings Park at 00 UTC 08 March 2006 2.5
2
1.5
1 Lantau Peak Altitude (km MSL) 0.5 U H 0 0 0 290 295 300 305 310 N NE E SE S SW W NW N 0 5 10 15 20 Potential Temperature (K) Wind Direction (deg) Wind Speed (m/s)
Regimes of strong terrain-induced winds at HKIA 12/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Introduction Radiosonde profile at Kings Park at 00 UTC 08 March 2006 2.5
2
1.5
1 Lantau Peak Altitude (km MSL) 0.5 U H 0 0 0 290 295 300 305 310 N NE E SE S SW W NW N 0 5 10 15 20 Potential Temperature (K) Wind Direction (deg) Wind Speed (m/s) Upstream conditions
I Layer height H0 = 520 m −1 I Wind speed U0 = 9 m s 0 ∆θ −2 I Reduced gravity g = g = 0.2 m s θ0 √ 0 I Froude number F0 = U0/ g H0 = 0.9 Regimes of strong terrain-induced winds at HKIA 13/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Introduction Radiosonde profile at Kings Park at 00 UTC 08 March 2006 2.5
2
1.5
1 Lantau Peak Altitude (km MSL) 0.5 U H 0 0 0 290 295 300 305 310 N NE E SE S SW W NW N 0 5 10 15 20 Potential Temperature (K) Wind Direction (deg) Wind Speed (m/s) Upstream conditions
I Layer height H0 = 520 m −1 I Wind speed U0 = 9 m s 0 ∆θ −2 I Reduced gravity g = g = 0.2 m s θ0 √ 0 I Froude number F0 = U0/ g H0 = 0.9 Regimes of strong terrain-induced winds at HKIA 14/78 Alexander Gohm I Figure shows 21 severe wind cases taken from the literature I Regime boundaries valid for 2D ridge (Houghton & Kashara, 1968) I Problem: boundaries not valid for real terrain!
Introduction Goals and Methods Results Conclusions Appendix Introduction Regime diagram based on Kings Park radiosonde data 3.5
3
2.5 (km) 0
H 2
1.5
1 Height of Lantau Peak Layer height
0.5 08 Mar 2006
0 0 0.5 1 1.5 2 2.5 F Froude number 0
Regimes of strong terrain-induced winds at HKIA 15/78 Alexander Gohm I Regime boundaries valid for 2D ridge (Houghton & Kashara, 1968) I Problem: boundaries not valid for real terrain!
Introduction Goals and Methods Results Conclusions Appendix Introduction Regime diagram based on Kings Park radiosonde data 3.5
3 21
2 2.5 (km)
0 20
H 2 5 7 1 8 1.5 9 6
10 1 19 Height of Lantau Peak 18 Layer height 16 4 15 3 1314 0.5 17 08 Mar 2006
0 0 0.5 1 1.5 2 2.5 F Froude number 0
I Figure shows 21 severe wind cases taken from the literature
Regimes of strong terrain-induced winds at HKIA 16/78 Alexander Gohm I Problem: boundaries not valid for real terrain!
Introduction Goals and Methods Results Conclusions Appendix Introduction Regime diagram based on Kings Park radiosonde data 3.5
3 21 subcritical, supercritical, hydraulic jumps no jumps no jumps 2 2.5 (km)
0 20
H 2 5 7 1 8 1.5 9 6
10 1 19 Height of Lantau Peak 18 Layer height 16 4 15 3 1314 0.5 17 08 Mar 2006 complete blocking 0 0 0.5 1 1.5 2 2.5 F Froude number 0
I Figure shows 21 severe wind cases taken from the literature I Regime boundaries valid for 2D ridge (Houghton & Kashara, 1968)
Regimes of strong terrain-induced winds at HKIA 17/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Introduction Regime diagram based on Kings Park radiosonde data 3.5
3 21 subcritical, supercritical, hydraulic jumps no jumps no jumps 2 2.5 (km)
0 20
H 2 5 7 1 8 1.5 9 6
10 1 19 Height of Lantau Peak 18 Layer height 16 4 15 3 1314 0.5 17 08 Mar 2006 complete blocking 0 0 0.5 1 1.5 2 2.5 F Froude number 0
I Figure shows 21 severe wind cases taken from the literature I Regime boundaries valid for 2D ridge (Houghton & Kashara, 1968) I Problem: boundaries not valid for real terrain!
Regimes of strong terrain-induced winds at HKIA 18/78 Alexander Gohm Goals
I Develop a regime diagram for the flow past Lantau Island
I Determine diagnostic measures to separate flow regimes
Methods
I Use a single-layer shallow water model
I Perform a large amount of simulations for various upstream conditions
Introduction Goals and Methods Results Conclusions Appendix Goals and Methods
Regimes of strong terrain-induced winds at HKIA 19/78 Alexander Gohm I Determine diagnostic measures to separate flow regimes
Methods
I Use a single-layer shallow water model
I Perform a large amount of simulations for various upstream conditions
Introduction Goals and Methods Results Conclusions Appendix Goals and Methods
Goals
I Develop a regime diagram for the flow past Lantau Island
Regimes of strong terrain-induced winds at HKIA 20/78 Alexander Gohm Methods
I Use a single-layer shallow water model
I Perform a large amount of simulations for various upstream conditions
Introduction Goals and Methods Results Conclusions Appendix Goals and Methods
Goals
I Develop a regime diagram for the flow past Lantau Island
I Determine diagnostic measures to separate flow regimes
Regimes of strong terrain-induced winds at HKIA 21/78 Alexander Gohm I Perform a large amount of simulations for various upstream conditions
Introduction Goals and Methods Results Conclusions Appendix Goals and Methods
Goals
I Develop a regime diagram for the flow past Lantau Island
I Determine diagnostic measures to separate flow regimes
Methods
I Use a single-layer shallow water model
Regimes of strong terrain-induced winds at HKIA 22/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Goals and Methods
Goals
I Develop a regime diagram for the flow past Lantau Island
I Determine diagnostic measures to separate flow regimes
Methods
I Use a single-layer shallow water model
I Perform a large amount of simulations for various upstream conditions
Regimes of strong terrain-induced winds at HKIA 23/78 Alexander Gohm I Layer height: H0 = 0.25 ... 4 km MSL
I Froude number: F0 = 0.1 ... 4.0
I Wind direction: wdir = SE, (S, E)
I Shallow-water model of Sch¨arand Smith (1993)
I Real terrain (ASTER DEM)
I Mesh-size ∆x = 200 m I Initial conditions:
⇒∼ 130 simulations per wdir
Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island
10 1000
900 5 HKIA 800
Check Lap Kok 700 0 600 Lantau Island −5 500 y (km) Tai Hom 400 −10 Sham 300
Lo Fu Tau 200 −15 Lantau Peak Sunset Peak 100 Tung Chung Gap flow −20 0 −15 −10 −5 0 5 10 15 x (km)
Regimes of strong terrain-induced winds at HKIA 24/78 Alexander Gohm I Layer height: H0 = 0.25 ... 4 km MSL
I Froude number: F0 = 0.1 ... 4.0
I Wind direction: wdir = SE, (S, E)
I Real terrain (ASTER DEM)
I Mesh-size ∆x = 200 m I Initial conditions:
⇒∼ 130 simulations per wdir
Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island I Shallow-water model of 10 1000 Sch¨arand Smith (1993)
900 5 HKIA 800
Check Lap Kok 700 0 600 Lantau Island −5 500 y (km) Tai Hom 400 −10 Sham 300
Lo Fu Tau 200 −15 Lantau Peak Sunset Peak 100 Tung Chung Gap flow −20 0 −15 −10 −5 0 5 10 15 x (km)
Regimes of strong terrain-induced winds at HKIA 25/78 Alexander Gohm I Layer height: H0 = 0.25 ... 4 km MSL
I Froude number: F0 = 0.1 ... 4.0
I Wind direction: wdir = SE, (S, E)
I Mesh-size ∆x = 200 m I Initial conditions:
⇒∼ 130 simulations per wdir
Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island I Shallow-water model of 10 1000 Sch¨arand Smith (1993)
900 I Real terrain (ASTER DEM) 5 HKIA 800
Check Lap Kok 700 0 600 Lantau Island −5 500 y (km) Tai Hom 400 −10 Sham 300
Lo Fu Tau 200 −15 Lantau Peak Sunset Peak 100 Tung Chung Gap flow −20 0 −15 −10 −5 0 5 10 15 x (km)
Regimes of strong terrain-induced winds at HKIA 26/78 Alexander Gohm I Layer height: H0 = 0.25 ... 4 km MSL
I Froude number: F0 = 0.1 ... 4.0
I Wind direction: wdir = SE, (S, E)
I Initial conditions:
⇒∼ 130 simulations per wdir
Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island I Shallow-water model of 10 1000 Sch¨arand Smith (1993)
900 I Real terrain (ASTER DEM) 5 HKIA 800 I Mesh-size ∆x = 200 m Check Lap Kok 700 0 600 Lantau Island −5 500 y (km) Tai Hom 400 −10 Sham 300
Lo Fu Tau 200 −15 Lantau Peak Sunset Peak 100 Tung Chung Gap flow −20 0 −15 −10 −5 0 5 10 15 x (km)
Regimes of strong terrain-induced winds at HKIA 27/78 Alexander Gohm I Layer height: H0 = 0.25 ... 4 km MSL
I Froude number: F0 = 0.1 ... 4.0
I Wind direction: wdir = SE, (S, E) ⇒∼ 130 simulations per wdir
Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island I Shallow-water model of 10 1000 Sch¨arand Smith (1993)
900 I Real terrain (ASTER DEM) 5 HKIA 800 I Mesh-size ∆x = 200 m Check Lap Kok 700 0 I Initial conditions: 600 Lantau Island −5 500 y (km) Tai Hom 400 −10 Sham 300
Lo Fu Tau 200 −15 Lantau Peak Sunset Peak 100 Tung Chung Gap flow −20 0 −15 −10 −5 0 5 10 15 x (km)
Regimes of strong terrain-induced winds at HKIA 28/78 Alexander Gohm I Froude number: F0 = 0.1 ... 4.0
I Wind direction: wdir = SE, (S, E) ⇒∼ 130 simulations per wdir
Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island I Shallow-water model of 10 1000 Sch¨arand Smith (1993)
900 I Real terrain (ASTER DEM) 5 HKIA 800 I Mesh-size ∆x = 200 m Check Lap Kok 700 0 I Initial conditions: 600 Lantau Island −5 500 I Layer height: y (km) Tai Hom 400 H0 = 0.25 ... 4 km MSL −10 Sham 300
Lo Fu Tau 200 −15 Lantau Peak Sunset Peak 100 Tung Chung Gap flow −20 0 −15 −10 −5 0 5 10 15 x (km)
Regimes of strong terrain-induced winds at HKIA 29/78 Alexander Gohm I Wind direction: wdir = SE, (S, E) ⇒∼ 130 simulations per wdir
Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island I Shallow-water model of 10 1000 Sch¨arand Smith (1993)
900 I Real terrain (ASTER DEM) 5 HKIA 800 I Mesh-size ∆x = 200 m Check Lap Kok 700 0 I Initial conditions: 600 Lantau Island −5 500 I Layer height: y (km) Tai Hom 400 H0 = 0.25 ... 4 km MSL −10 Sham 300 I Froude number: F = 0.1 ... 4.0 Lo Fu Tau 200 0 −15 Lantau Peak Sunset Peak 100 Tung Chung Gap flow −20 0 −15 −10 −5 0 5 10 15 x (km)
Regimes of strong terrain-induced winds at HKIA 30/78 Alexander Gohm ⇒∼ 130 simulations per wdir
Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island I Shallow-water model of 10 1000 Sch¨arand Smith (1993)
900 I Real terrain (ASTER DEM) 5 HKIA 800 I Mesh-size ∆x = 200 m Check Lap Kok 700 0 I Initial conditions: 600 Lantau Island −5 500 I Layer height: y (km) Tai Hom 400 H0 = 0.25 ... 4 km MSL −10 Sham 300 I Froude number: F = 0.1 ... 4.0 Lo Fu Tau 200 0 −15 Lantau Peak Sunset Peak 100 I Wind direction: Tung Chung Gap flow −20 0 wdir = SE, (S, E) −15 −10 −5 0 5 10 15 x (km)
Regimes of strong terrain-induced winds at HKIA 31/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Model setup
Lantau Island I Shallow-water model of 10 1000 Sch¨arand Smith (1993)
900 I Real terrain (ASTER DEM) 5 HKIA 800 I Mesh-size ∆x = 200 m Check Lap Kok 700 0 I Initial conditions: 600 Lantau Island −5 500 I Layer height: y (km) Tai Hom 400 H0 = 0.25 ... 4 km MSL −10 Sham 300 I Froude number: F = 0.1 ... 4.0 Lo Fu Tau 200 0 −15 Lantau Peak Sunset Peak 100 I Wind direction: Tung Chung Gap flow −20 0 wdir = SE, (S, E) −15 −10 −5 0 5 10 15 x (km) ⇒∼ 130 simulations per wdir
Regimes of strong terrain-induced winds at HKIA 32/78 Alexander Gohm Regime diagram 4.5 subcritical (I) 4
3.5
3 (km) 0
H 2.5
2
1.5
Layer height 1
0.5
0 0 0.5 1 1.5 2 2.5 3 3.5 4 F Froude number 0
I subcritical flow (F < 1) everywhere I weak flow to the lee I no vorticity production, no shear lines
Introduction Goals and Methods Results Conclusions Appendix Regime I: subcritial everywhere
F0 = 0.4, H0 = 2.0 km Local Froude number F 15 >2.0
10
1.5 5
0 1.0 y (km) −5
−10 0.5
−15
−20 0 −20 −15 −10 −5 0 5 10 15 20 x (km)
Regimes of strong terrain-induced winds at HKIA 33/78 Alexander Gohm I subcritical flow (F < 1) everywhere I weak flow to the lee I no vorticity production, no shear lines
Introduction Goals and Methods Results Conclusions Appendix Regime I: subcritial everywhere
F0 = 0.4, H0 = 2.0 km Local Froude number F Regime diagram 15 >2.0 4.5 subcritical (I) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
Regimes of strong terrain-induced winds at HKIA 34/78 Alexander Gohm I weak flow to the lee I no vorticity production, no shear lines
Introduction Goals and Methods Results Conclusions Appendix Regime I: subcritial everywhere
F0 = 0.4, H0 = 2.0 km Local Froude number F Regime diagram 15 >2.0 4.5 subcritical (I) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I subcritical flow (F < 1) everywhere
Regimes of strong terrain-induced winds at HKIA 35/78 Alexander Gohm I no vorticity production, no shear lines
Introduction Goals and Methods Results Conclusions Appendix Regime I: subcritial everywhere
F0 = 0.4, H0 = 2.0 km Local Froude number F Regime diagram 15 >2.0 4.5 subcritical (I) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I subcritical flow (F < 1) everywhere I weak flow to the lee
Regimes of strong terrain-induced winds at HKIA 36/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime I: subcritial everywhere
F0 = 0.4, H0 = 2.0 km Local Froude number F Regime diagram 15 >2.0 4.5 subcritical (I) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I subcritical flow (F < 1) everywhere I weak flow to the lee I no vorticity production, no shear lines
Regimes of strong terrain-induced winds at HKIA 37/78 Alexander Gohm I subcritical flow (F < 1) in the airport region I stationary hydraulic jump over lee slope I weak vorticity production and straight shearlines
Introduction Goals and Methods Results Conclusions Appendix Regime II: stable wake
F0 = 0.8, H0 = 1.5 km Local Froude number F Regime diagram 15 >2.0 4.5 stable wake (II) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
Regimes of strong terrain-induced winds at HKIA 38/78 Alexander Gohm I stationary hydraulic jump over lee slope I weak vorticity production and straight shearlines
Introduction Goals and Methods Results Conclusions Appendix Regime II: stable wake
F0 = 0.8, H0 = 1.5 km Local Froude number F Regime diagram 15 >2.0 4.5 stable wake (II) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I subcritical flow (F < 1) in the airport region
Regimes of strong terrain-induced winds at HKIA 39/78 Alexander Gohm I weak vorticity production and straight shearlines
Introduction Goals and Methods Results Conclusions Appendix Regime II: stable wake
F0 = 0.8, H0 = 1.5 km Local Froude number F Regime diagram 15 >2.0 4.5 stable wake (II) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I subcritical flow (F < 1) in the airport region I stationary hydraulic jump over lee slope
Regimes of strong terrain-induced winds at HKIA 40/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime II: stable wake
F0 = 0.8, H0 = 1.5 km Local Froude number F Regime diagram 15 >2.0 4.5 stable wake (II) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I subcritical flow (F < 1) in the airport region I stationary hydraulic jump over lee slope I weak vorticity production and straight shearlines
Regimes of strong terrain-induced winds at HKIA 41/78 Alexander Gohm I supercritical flow (F > 1) in the airport region I stationary V-shaped jumps I only weak vorticity production
Introduction Goals and Methods Results Conclusions Appendix Regime III: V-shaped hydraulic jumps
F0 = 1.4, H0 = 1.0 km Local Froude number F Regime diagram 15 >2.0 4.5 V−shaped jumps (III) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
Regimes of strong terrain-induced winds at HKIA 42/78 Alexander Gohm I stationary V-shaped jumps I only weak vorticity production
Introduction Goals and Methods Results Conclusions Appendix Regime III: V-shaped hydraulic jumps
F0 = 1.4, H0 = 1.0 km Local Froude number F Regime diagram 15 >2.0 4.5 V−shaped jumps (III) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I supercritical flow (F > 1) in the airport region
Regimes of strong terrain-induced winds at HKIA 43/78 Alexander Gohm I only weak vorticity production
Introduction Goals and Methods Results Conclusions Appendix Regime III: V-shaped hydraulic jumps
F0 = 1.4, H0 = 1.0 km Local Froude number F Regime diagram 15 >2.0 4.5 V−shaped jumps (III) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I supercritical flow (F > 1) in the airport region I stationary V-shaped jumps
Regimes of strong terrain-induced winds at HKIA 44/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime III: V-shaped hydraulic jumps
F0 = 1.4, H0 = 1.0 km Local Froude number F Regime diagram 15 >2.0 4.5 V−shaped jumps (III) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I supercritical flow (F > 1) in the airport region I stationary V-shaped jumps I only weak vorticity production
Regimes of strong terrain-induced winds at HKIA 45/78 Alexander Gohm I supercritical flow (F > 1) everywhere I no hydraulic jumps I slightly weaker flow near V-waves
Introduction Goals and Methods Results Conclusions Appendix Regime IV: supercritial everywhere
F0 = 2.0, H0 = 1.5 km Local Froude number F Regime diagram 15 >2.0 4.5 supercritical (IV) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
Regimes of strong terrain-induced winds at HKIA 46/78 Alexander Gohm I no hydraulic jumps I slightly weaker flow near V-waves
Introduction Goals and Methods Results Conclusions Appendix Regime IV: supercritial everywhere
F0 = 2.0, H0 = 1.5 km Local Froude number F Regime diagram 15 >2.0 4.5 supercritical (IV) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I supercritical flow (F > 1) everywhere
Regimes of strong terrain-induced winds at HKIA 47/78 Alexander Gohm I slightly weaker flow near V-waves
Introduction Goals and Methods Results Conclusions Appendix Regime IV: supercritial everywhere
F0 = 2.0, H0 = 1.5 km Local Froude number F Regime diagram 15 >2.0 4.5 supercritical (IV) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I supercritical flow (F > 1) everywhere I no hydraulic jumps
Regimes of strong terrain-induced winds at HKIA 48/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime IV: supercritial everywhere
F0 = 2.0, H0 = 1.5 km Local Froude number F Regime diagram 15 >2.0 4.5 supercritical (IV) 4 10 3.5 1.5 5 3 (km) 0
0 H 2.5 1.0 y (km) −5 2
1.5 −10
0.5 Layer height 1 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I supercritical flow (F > 1) everywhere I no hydraulic jumps I slightly weaker flow near V-waves
Regimes of strong terrain-induced winds at HKIA 49/78 Alexander Gohm I mountains higher than fluid layer → “dry” areas I large vortices (∼ 10 km) and shear lines near edges of island I airport located in wake region
Introduction Goals and Methods Results Conclusions Appendix Regime V: flow around – vortex shedding
F0 = 0.8, H0 = 0.25 km Vorticity ζˆ Regime diagram 15 >1.5 4.5 flow around (V) 4 10 1.0 3.5 5 3
0.5 (km) 0
0 H 2.5 0
y (km) 2 −5
−0.5 1.5 −10 Layer height 1 −1.0 −15 0.5
−20 <−1.5 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
Regimes of strong terrain-induced winds at HKIA 50/78 Alexander Gohm I large vortices (∼ 10 km) and shear lines near edges of island I airport located in wake region
Introduction Goals and Methods Results Conclusions Appendix Regime V: flow around – vortex shedding
F0 = 0.8, H0 = 0.25 km Vorticity ζˆ Regime diagram 15 >1.5 4.5 flow around (V) 4 10 1.0 3.5 5 3
0.5 (km) 0
0 H 2.5 0
y (km) 2 −5
−0.5 1.5 −10 Layer height 1 −1.0 −15 0.5
−20 <−1.5 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I mountains higher than fluid layer → “dry” areas
Regimes of strong terrain-induced winds at HKIA 51/78 Alexander Gohm I airport located in wake region
Introduction Goals and Methods Results Conclusions Appendix Regime V: flow around – vortex shedding
F0 = 0.8, H0 = 0.25 km Vorticity ζˆ Regime diagram 15 >1.5 4.5 flow around (V) 4 10 1.0 3.5 5 3
0.5 (km) 0
0 H 2.5 0
y (km) 2 −5
−0.5 1.5 −10 Layer height 1 −1.0 −15 0.5
−20 <−1.5 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I mountains higher than fluid layer → “dry” areas I large vortices (∼ 10 km) and shear lines near edges of island
Regimes of strong terrain-induced winds at HKIA 52/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime V: flow around – vortex shedding
F0 = 0.8, H0 = 0.25 km Vorticity ζˆ Regime diagram 15 >1.5 4.5 flow around (V) 4 10 1.0 3.5 5 3
0.5 (km) 0
0 H 2.5 0
y (km) 2 −5
−0.5 1.5 −10 Layer height 1 −1.0 −15 0.5
−20 <−1.5 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I mountains higher than fluid layer → “dry” areas I large vortices (∼ 10 km) and shear lines near edges of island I airport located in wake region
Regimes of strong terrain-induced winds at HKIA 53/78 Alexander Gohm I stationary hydraulic jump close to the crest I airport affect by vortex shedding I vortex size ∼ 5 km, shedding period ∼ 30 to 50 min
Introduction Goals and Methods Results Conclusions Appendix Regime VI: unstable wake – vortex shedding
F0 = 0.4, H0 = 1.0 km Vorticity ζˆ Regime diagram 15 >1.0 4.5 unstable wake (VI) 0.8 4 10 0.6 3.5
5 0.4 3 (km) 0
0.2 H 0 2.5 0
y (km) 2 −5 −0.2 1.5 −10 −0.4 Layer height 1 −0.6 −15 −0.8 0.5
−20 <−1.0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
Regimes of strong terrain-induced winds at HKIA 54/78 Alexander Gohm I airport affect by vortex shedding I vortex size ∼ 5 km, shedding period ∼ 30 to 50 min
Introduction Goals and Methods Results Conclusions Appendix Regime VI: unstable wake – vortex shedding
F0 = 0.4, H0 = 1.0 km Vorticity ζˆ Regime diagram 15 >1.0 4.5 unstable wake (VI) 0.8 4 10 0.6 3.5
5 0.4 3 (km) 0
0.2 H 0 2.5 0
y (km) 2 −5 −0.2 1.5 −10 −0.4 Layer height 1 −0.6 −15 −0.8 0.5
−20 <−1.0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I stationary hydraulic jump close to the crest
Regimes of strong terrain-induced winds at HKIA 55/78 Alexander Gohm I vortex size ∼ 5 km, shedding period ∼ 30 to 50 min
Introduction Goals and Methods Results Conclusions Appendix Regime VI: unstable wake – vortex shedding
F0 = 0.4, H0 = 1.0 km Vorticity ζˆ Regime diagram 15 >1.0 4.5 unstable wake (VI) 0.8 4 10 0.6 3.5
5 0.4 3 (km) 0
0.2 H 0 2.5 0
y (km) 2 −5 −0.2 1.5 −10 −0.4 Layer height 1 −0.6 −15 −0.8 0.5
−20 <−1.0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I stationary hydraulic jump close to the crest I airport affect by vortex shedding
Regimes of strong terrain-induced winds at HKIA 56/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime VI: unstable wake – vortex shedding
F0 = 0.4, H0 = 1.0 km Vorticity ζˆ Regime diagram 15 >1.0 4.5 unstable wake (VI) 0.8 4 10 0.6 3.5
5 0.4 3 (km) 0
0.2 H 0 2.5 0
y (km) 2 −5 −0.2 1.5 −10 −0.4 Layer height 1 −0.6 −15 −0.8 0.5
−20 <−1.0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I stationary hydraulic jump close to the crest I airport affect by vortex shedding I vortex size ∼ 5 km, shedding period ∼ 30 to 50 min
Regimes of strong terrain-induced winds at HKIA 57/78 Alexander Gohm I stationary hydraulic jump near foot of mountain I larger region affect by vortex shedding I vortex size ∼ 2 km, shedding period ∼ 20 min
Introduction Goals and Methods Results Conclusions Appendix Regime VI: unstable wake – vortex shedding
F0 = 0.8, H0 = 1.0 km Vorticity ζˆ Regime diagram 15 >1.0 4.5 unstable wake (VI) 0.8 4 10 0.6 3.5
5 0.4 3 (km) 0
0.2 H 0 2.5 0
y (km) 2 −5 −0.2 1.5 −10 −0.4 Layer height 1 −0.6 −15 −0.8 0.5
−20 <−1.0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
Regimes of strong terrain-induced winds at HKIA 58/78 Alexander Gohm I larger region affect by vortex shedding I vortex size ∼ 2 km, shedding period ∼ 20 min
Introduction Goals and Methods Results Conclusions Appendix Regime VI: unstable wake – vortex shedding
F0 = 0.8, H0 = 1.0 km Vorticity ζˆ Regime diagram 15 >1.0 4.5 unstable wake (VI) 0.8 4 10 0.6 3.5
5 0.4 3 (km) 0
0.2 H 0 2.5 0
y (km) 2 −5 −0.2 1.5 −10 −0.4 Layer height 1 −0.6 −15 −0.8 0.5
−20 <−1.0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I stationary hydraulic jump near foot of mountain
Regimes of strong terrain-induced winds at HKIA 59/78 Alexander Gohm I vortex size ∼ 2 km, shedding period ∼ 20 min
Introduction Goals and Methods Results Conclusions Appendix Regime VI: unstable wake – vortex shedding
F0 = 0.8, H0 = 1.0 km Vorticity ζˆ Regime diagram 15 >1.0 4.5 unstable wake (VI) 0.8 4 10 0.6 3.5
5 0.4 3 (km) 0
0.2 H 0 2.5 0
y (km) 2 −5 −0.2 1.5 −10 −0.4 Layer height 1 −0.6 −15 −0.8 0.5
−20 <−1.0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I stationary hydraulic jump near foot of mountain I larger region affect by vortex shedding
Regimes of strong terrain-induced winds at HKIA 60/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime VI: unstable wake – vortex shedding
F0 = 0.8, H0 = 1.0 km Vorticity ζˆ Regime diagram 15 >1.0 4.5 unstable wake (VI) 0.8 4 10 0.6 3.5
5 0.4 3 (km) 0
0.2 H 0 2.5 0
y (km) 2 −5 −0.2 1.5 −10 −0.4 Layer height 1 −0.6 −15 −0.8 0.5
−20 <−1.0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I stationary hydraulic jump near foot of mountain I larger region affect by vortex shedding I vortex size ∼ 2 km, shedding period ∼ 20 min
Regimes of strong terrain-induced winds at HKIA 61/78 Alexander Gohm I gap winds occur for several different flow regimes I up to three gap jets I airport affected by two gap jets
Introduction Goals and Methods Results Conclusions Appendix Regimes with gap winds
F0 = 0.6, H0 = 0.75 km Wind speed wspdˆ Regime diagram 15 >1.2 4.5 gap winds 4 10 1.0 3.5 5 0.8 3 (km) 0
0 H 2.5 0.6
y (km) 2 −5
0.4 1.5 −10 Layer height 1 0.2 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
Regimes of strong terrain-induced winds at HKIA 62/78 Alexander Gohm I up to three gap jets I airport affected by two gap jets
Introduction Goals and Methods Results Conclusions Appendix Regimes with gap winds
F0 = 0.6, H0 = 0.75 km Wind speed wspdˆ Regime diagram 15 >1.2 4.5 gap winds 4 10 1.0 3.5 5 0.8 3 (km) 0
0 H 2.5 0.6
y (km) 2 −5
0.4 1.5 −10 Layer height 1 0.2 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I gap winds occur for several different flow regimes
Regimes of strong terrain-induced winds at HKIA 63/78 Alexander Gohm I airport affected by two gap jets
Introduction Goals and Methods Results Conclusions Appendix Regimes with gap winds
F0 = 0.6, H0 = 0.75 km Wind speed wspdˆ Regime diagram 15 >1.2 4.5 gap winds 4 10 1.0 3.5 5 0.8 3 (km) 0
0 H 2.5 0.6
y (km) 2 −5
0.4 1.5 −10 Layer height 1 0.2 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I gap winds occur for several different flow regimes I up to three gap jets
Regimes of strong terrain-induced winds at HKIA 64/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regimes with gap winds
F0 = 0.6, H0 = 0.75 km Wind speed wspdˆ Regime diagram 15 >1.2 4.5 gap winds 4 10 1.0 3.5 5 0.8 3 (km) 0
0 H 2.5 0.6
y (km) 2 −5
0.4 1.5 −10 Layer height 1 0.2 −15 0.5
−20 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −20 −15 −10 −5 0 5 10 15 20 F x (km) Froude number 0
I gap winds occur for several different flow regimes I up to three gap jets I airport affected by two gap jets
Regimes of strong terrain-induced winds at HKIA 65/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regimes with gap winds – close-up
F0 = 0.6, H0 = 0.75 km Wind speed wspdˆ Regime diagram 6 >1.2 4.5 gap winds 4 4 1.0 2 3.5
0 0.8 3 (km) 0 H −2 2.5 0.6
y (km) −4 2
−6 0.4 1.5 Layer height −8 1 0.2 −10 0.5
−12 0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 −10 −5 0 5 10 Froude number F x (km) 0
I gap winds occur for several different flow regimes I up to three gap jets I airport affected by two gap jets
Regimes of strong terrain-induced winds at HKIA 66/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime diagram
Deriving average quantities in domain D1
10 1000
900 5 HKIA 800
700 0 D1 600
−5 500
y (km) D2 400
−10 300 D3 200 −15 100
−20 0 −15 −10 −5 0 5 10 15 x (km) Regimes of strong terrain-induced winds at HKIA 67/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime diagram 1 −3 −1 Vorticity (10 s ) in domain D1 4.5 >5 subcritical (I) 4 stable wake (II) V−shaped jumps (III) 4 3.5 supercritical (IV) flow around (V) 3 (km) unstable wake (VI) 0 3 H 2.5 gap winds
2 2 1.5
Layer height 1 1
0.5
0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 F Froude number 0
s t 1Mean absolute value of vorticity abs(ζ) × 103 Regimes of strong terrain-induced winds at HKIA 68/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime diagram
2 −1 Temporal variability of wind speed (m s ) in domain D1 4.5 >2.0 subcritical (I) 4 stable wake (II) V−shaped jumps (III) 3.5 supercritical (IV) 1.5 flow around (V) 3 (km) unstable wake (VI) 0
H 2.5 gap winds 1.0 2
1.5
Layer height 0.5 1
0.5
0 0 0 0.5 1 1.5 2 2.5 3 3.5 4 F Froude number 0
2 s Standard deviation in time of wind speed σt (wspd) Regimes of strong terrain-induced winds at HKIA 69/78 Alexander Gohm I Derived a regime diagram for terrain-induced winds at HKIA
I Can be used as a poor man’s forecasting tool
I Can be easily extended for other wind directions
I Should be verified with 3D model for selected regimes
Introduction Goals and Methods Results Conclusions Appendix Conclusions
Regimes of strong terrain-induced winds at HKIA 70/78 Alexander Gohm I Can be used as a poor man’s forecasting tool
I Can be easily extended for other wind directions
I Should be verified with 3D model for selected regimes
Introduction Goals and Methods Results Conclusions Appendix Conclusions
I Derived a regime diagram for terrain-induced winds at HKIA
Regimes of strong terrain-induced winds at HKIA 71/78 Alexander Gohm I Can be easily extended for other wind directions
I Should be verified with 3D model for selected regimes
Introduction Goals and Methods Results Conclusions Appendix Conclusions
I Derived a regime diagram for terrain-induced winds at HKIA
I Can be used as a poor man’s forecasting tool
Regimes of strong terrain-induced winds at HKIA 72/78 Alexander Gohm I Should be verified with 3D model for selected regimes
Introduction Goals and Methods Results Conclusions Appendix Conclusions
I Derived a regime diagram for terrain-induced winds at HKIA
I Can be used as a poor man’s forecasting tool
I Can be easily extended for other wind directions
Regimes of strong terrain-induced winds at HKIA 73/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Conclusions
I Derived a regime diagram for terrain-induced winds at HKIA
I Can be used as a poor man’s forecasting tool
I Can be easily extended for other wind directions
I Should be verified with 3D model for selected regimes
Regimes of strong terrain-induced winds at HKIA 74/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime diagram 3 Vorticity in domain D1 for different flow directions 4.5 East 3x10−3 s−1 4 East 5x10−3 s−1 Southeast 3x10−3 s−1 3.5 Southeast 5x10−3 s−1 −3 −1 3 South 3x10 s (km) −3 −1 0 South 5x10 s H 2.5
2
1.5
Layer height 1
0.5
0 0 0.5 1 1.5 2 2.5 3 3.5 4 F Froude number 0
s t 3Mean absolute value of vorticity abs(ζ) Regimes of strong terrain-induced winds at HKIA 75/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Regime diagram
A measure of acceleration
Mean wind speed in D1 Mean wind speed in D2 (HKIA area) normalized with D3 (lee slope) normalized with D3 4 >1.8 4 >1.8 subcritical (I) subcritical (I) 3.5 stable wake (II) 1.7 3.5 stable wake (II) 1.7 V−shaped jumps (III) V−shaped jumps (III) 3 supercritical (IV) 1.6 3 supercritical (IV) 1.6 flow around (V) flow around (V)
(km) unstable wake (VI) (km) unstable wake (VI) 0 2.5 1.5 0 2.5 1.5
H gap winds H gap winds 2 1.4 2 1.4
1.5 1.3 1.5 1.3
Layer height 1 1.2 Layer height 1 1.2
0.5 1.1 0.5 1.1
0 <1.0 0 <1.0 0 0.5 1 1.5 2 2.5 3 3.5 4 0 0.5 1 1.5 2 2.5 3 3.5 4 F F Froude number 0 Froude number 0
Regimes of strong terrain-induced winds at HKIA 76/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Appendix Deriving average quantities for regime diagram
I Averaging in space and time:
M s 1 X φ = φ , (x , y ) ∈ D , k = 1, 2, 3 (1) M i i i k i=1 N t 1 X φ = φ , ˆt ∈ (500, 510,..., 600) (2) N j j j=1
I Standard deviation in space and time: v u M u 1 X s σ (φ) = t (φ − φ )2, (x , y ) ∈ D , k = 1, 2, 3 (3) s M i i i k i=1 v u N t u 1 X 2 σt (φ) = t (φi − φ ) , ˆtj ∈ (500, 510,..., 600) (4) N j=1 Regimes of strong terrain-induced winds at HKIA 77/78 Alexander Gohm Introduction Goals and Methods Results Conclusions Appendix Appendix
Dimensionalization
I Length scale: L = 1000 m √ 0 I Velocity scale: g H0 0 −2 I Reduced gravity: g = 0.25 m s ˆ ∂vˆ ∂uˆ I Non-dimensional vorticity: ζ = ∂xˆ − ∂yˆ √ 0 I Dimensional vorticity: ζ = ζˆ g H0/L √ 0 I Dimensional wind speed: wspd = wspdˆ g H0
Regimes of strong terrain-induced winds at HKIA 78/78 Alexander Gohm