14 johnny cheung

7/24/2019 14 Johnny Cheung

1/41

IAHR-HK Student Research Forum, November 17, 2012

A Study on Storm Surge and Wave for Hong Kong Using

Different Typhoon Wind Field Models and Best Track Data

Johnny Kai-Chun CHEUNG, Dr. Ander CHOW

ARUP, HKSAR, China

Abstract: Located at the northern coast of the South China Sea one of the most

active typical cyclone sub-basins in the world Hong Kong is often threatened bystorm surge and wave due to the approaching tropical cyclones, causing sea water

inundation and damages of coastal structures.

Nowadays, sea wall is still the main solution to protect the city from storm surge and

wave. Hence, estimation of sea wall height is a major issue. The wall might not be

able to cope with storm surge and wave if it is too low. On the other hand, the

construction and maintenance fee would be very high if it is too high. Typically, the

height of the wall was designed using a combination of wave height, astronomical tide

level and storm surge near the site. However, only very limited observation data was

available for design and this would affect the reliability and safety of the coastal

structures. Therefore, estimation of storm surge and wave of interested area is

important for planning and designing effective coastal protective works and strategies.

Numerical hydrodynamic model is one of the tools that can be used to estimate both

the storm surge and wave under different tropical cyclone conditions for the designworks. The results are simulated by putting a wind field which describes the typhoon

wind speed, wind direction and pressure of the modelled area into the hydrodynamic

model. The wind field can be generated by several typhoon models using the tropical

cyclone tracks data. The data are called best track data and each observatory agent

provides its own best track data for each cyclone event. The data include times,

tropical cyclone centre locations, maximum sustained wind speeds, minimum centre

pressures and the maximum wind radii at six-hour intervals. To achieve accurate

results, precise descriptions of wind and pressure of the typhoon wind field would bea key element. The objective of this paper is to study the best typhoon model and best

track data for Hong Kong by computing and comparing the storm surge and wave of

different typical cyclone events for Hong Kong with the measured data.

In this paper different wind fields based on different wind models were generated


2/41

A Study on Storm Surge and Wave for Hong Kong Using Different

Typhoon Wind Field Models and Best Track Data

Cheung Kai Chun, Johnny

Supervisor: Dr. Ander Chow


3/41

2

Contents

Background & Motivation

Result and Discussion

Conclusion


4/41

3

STORMTropicalcyclone

Background


5/41

4

On average, about 6 to 7 tropical cyclones affect Hong Kong each year

Tropical Cyclone Tracks Entering the 300 km range of Hong Kong (1951-2011)


6/41

5

Tropical Cyclone Track Information

Background

MaximumWind

Radius

MaximumSustainedWindSpeed

CycloneEye

Location

MinimumCentre

PressureTime

Best TrackData


7/41

6

Hong KongObservatory

(HKO)

Japan

MetrologicalAgency (JMA)

Joint TyphoonWarningCenter

(JTWC)

Background

Significant difference

were found between best

track data provided by

different agents


8/41

7

SURGE

Background

The differences between water

level and astronomical tide.


9/41

8

Storm Surge

Generated by tropical cyclone

Background

Pressure

Relative low pressure at the centre of

tropical cyclone

Pressure driven surge

(5% of total)

Wind driven surge

Cyclone direction Deep water region: water

flows without raising sea

level too much

Storm Surge = Storm Water Level (Measured) Normal Water Level (Predict)


10/41

9

Wave

Combination of swells and local wind waves

Background

WAVE PERIOD WAVELENGTH WAVE TYPE CAUSE

Capillary < 0.1 sec < 2 cm deep to shallow local winds

Chop 1-10 sec 1-10 m deep to shallow local winds

Swell 10-30 sec up to hundreds of m deep or shallow distant storm

Seiche 10 min-10 hr up to hundreds of km shallow or intermediate wind, tsunami, tidal

resonance

Tsunami 10-60 min up to hundreds of km shallow or intermediate

earthquakes or volcanic

eruptions under (or near) the

ocean

Tide 12.4-24.8 hr thousands of km shallow gravitational attraction of sun

and moon


11/41

10 Background

Storm Surge

Maximum Storm Surge Maximum Storm Tide Level

Station

Maximum sea level

(above chart datum)

Maximum storm surge

(above astronomical tide)

Height (m) Date/Month Time Height (m) Date/Month Time

Quarry Bay 2.76 24/7 01:48 1.11 24/7 01:48

Shek Pik 3.19 24/7 02:08 1.47 24/7 02:08

Tai Miu Wan 2.78 24/7 01:45 1.19 24/7 01:45

Tai Po Kau 3.09 24/7 01:53 1.47 24/7 03:24

Tsim Bei Tsui 3.23 24/7 03:46 1.51 24/7 03:46


12/41

11

Damages Brought By Storm Surge and Wave

Background

Serious inundation in Tai O due to the

combination of storm surge and high tide(Typhoon Hagupit, 2008)


13/41

12

Solution?

Background

Tai O Seawall


14/41

13

Couple Flow-Wave Hydrodynamic Model

Background

Typhoon Wind Field:

Generated by typhoon

wind model

Describe the wind and

pressure of the

modelled area

Main driving force of

the model!

Significant Wave Height Storm Surge


15/41

14

Typhoon Wind Model

Background

Convert Best Track Data into the wind speed and pressure at a specific location

Popular models : Young, Holland, Rankine, etc

Best Track Data

Typhoon Wind Field for modelling

works

Typhoon Wind Model


16/41

15

Objective

Objective

Goal: To find the Best Typhoon Model and Best Track Datafor Hong Kong

Strom Surge and

Wave ModelledResult

TyphoonWindField

Model

Best TrackData


17/41

16

Methodology Outline

Methodology Outline

The Best Typhoon Model

and Best Track Data for

Hong Kong were selected

based on the smallest %

Error and % RMS Error

Best TrackData (HKO &

JTWC)

TyphoonWind Field

HydrodynamicModel

StormSurge and

WaveResult

Typhoon Wind Field Model

(Young & Holland)

Coupled Flow-

Wave Model(Delft 3D

SWAN)

Compare With

Observation Data


18/41

17

Modelled Typical Cyclone Tracks

Modelled Tracks

Hong Kong


19/41

18

Best Track Data

Best Track Data

Joint Typhoon Warning Center (JTWC)Hong Kong Observatory (HKO)

HKO JTWC

Time UTC UTCInterval 6 hour 6 hour

Maximum

Sustained Wind 10 min averaged 1 min averaged


20/41

19

Best Track Data Comparison

Best Track Data

y = 0.7673x + 10.179R = 0.8142

10

15

20

25

30

35

40

45

50

55

60

10 15 20 25 30 35 40 45 50 55 60

HKO10

-minWindSpeed(m/s)

JTWC 10-min Wind Speed (m/s)

y = 0.8516x + 139.58

R = 0.849

920

930

940

950

960

970

980

990

1000

920 930 940 950 960 970 980 990 1000

HKO

Pressure(hPa)

JTWC Pressure (hPa)

Wind Speed Comparison

Center Pressure Comparison

JTWC ~ 1.3 HKO

JTWC ~ 1.13HKO


21/41

20

Typhoon Wind Field

Typhoon Wind Model

Wind Field Required Parameters

Radial distance fromthe storms center, r Max WindRadius, RmwCenter Pressure,Pc

Max Sustained WindSpeed, Vmax

Young

Holland

Young (1981)

where B = 1.5 + (980-Pc)/120

Holland (1980)


22/41

21

Couple Flow-Wave Model (Delft3D SWAN)

Curvi-linear grid

Wind forcing by typhoon wind field

Boundary Condition = HK MSL

Model Built


23/41

22

Bathymetry

South China Sea ENC

HK ENC

Paper Charts

Model Built


24/41

23

Model Train

Model Train

Delft 3D

SWAN

- Water Level- Current

- Wind Field

Radiation Stress

Maximum 15 iterations

Time Steps 1 Minute Every 60 minutesEvery 60 minutes

- Bathymetry

- Boundary Condition (HK

MSL)- Computational grid

- Time frame

- Typhoon Wind field

Initial

Water LevelCurrentetc

Every 60 minutes

Significant Wave Height

Peak Periodetc

Output

Every 60 minutes

Output


25/41

24

Model Runs

Tropical Cyclone Name(ID) Wind ModelUsed Best Track Data Used Name of the Run

Imbudo (200307)

Holland JTWC Imbudo_Holland_JTWC

Holland HKO Imbudo_Holland_HKO

Young JTWC Imbudo_Young_JTWC

Young HKO Imbudo_Young_HKO

Prapiroon (200606)

Holland JTWC Prapiroon_Holland_JTWC

Holland HKO Prapiroon_Holland_HKO

Young JTWC Prapiroon_Young_JTWC

Young HKO Prapiroon_Young_HKO

Nuri (200812)

Holland JTWC Nuri_Holland_JTWC

Holland HKO Nuri_Holland_HKO

Young JTWC Nuri_Young_JTWC

Young HKO Nuri_Young_HKO

Hagupit (200814)

Holland JTWC Hagupit_Holland_JTWC

Holland HKO Hagupit_Holland_HKO

Young JTWC Hagupit_Young_JTWC

Young HKO Hagupit_Young_HKO

Model Runs


26/41

25

Result Snap Shots Hagupit_Young_JTWC

Result and Discussion Snap Shots

Storm Surge Water was pushed toward Macau

23 Sep 2008 1900 UTC23 Sep 2008 1400 UTC23 Sep 2008 0900 UTC

23 Sep 2008 1900 UTC23 Sep 2008 1400 UTC23 Sep 2008 0900 UTC

Significant Wave Height Huge waves were blocked by the Lema Islands


27/41

26

Animations HAGUPIT_Young_JTWC

Result and Discussion Animation

Track+Wind Field


28/41

27



Significant Wave Height


29/41

28



Storm Surge


30/41

29 Result and Discussion QUB Station

Tropical Cyclone

Name (ID) Name of the Run Max Storm Surge (m) Time % Error

Time Difference

(hh:mm)

Imbudo (200307)

Observation 1.02 24/7/2003 2:31

Holland_JTWC 0.28 23/7/2003 20:00 -72.9% 06:31

Holland_HKO 0.46 24/7/2003 5:00 -55.2% 02:29

Young_JTWC 0.44 23/7/2003 20:00 -57.3% 06:31

Young_HKO 0.61 24/7/2003 5:00 -40.3% 02:29

Prapiroon (200606)

Observation 0.64 3/8/2006 17:48

Holland_JTWC 0.21 3/8/2006 2:00 -67.6% 15:48

Holland_HKO 0.24 3/8/2006 12:00 -63.0% 05:48

Young_JTWC 0.25 3/8/2006 10:00 -61.5% 07:48

Young_HKO 0.29 3/8/2006 10:00 -55.0% 07:48

Nuri (200812)

Observation 0.56 22/8/2008 11:10

Holland_JTWC 0.38 22/8/2008 20:00 -32.6% 08:50

Holland_HKO 0.44 22/8/2008 20:00 -20.9% 08:50

Young_JTWC 0.33 22/8/2008 15:00 -40.9% 03:50

Young_HKO 0.44 22/8/2008 20:00 -21.8% 08:50

Hagupit (200814)

Observation 1.43 24/9/2008 00:54Holland_JTWC 1.34 23/9/2008 22:00 -6.4% 02:54

Holland_HKO 1.02 23/9/2008 23:00 -28.4% 01:54

Young_JTWC 2.12 23/9/2008 23:00 48.3% 01:54

Young_HKO 1.17 23/9/2008 23:00 -18.4% 01:54

QUB Station Storm Surge Results


31/41

30 Result and Discussion TPK Station

Tropical Cyclone

Name (ID) Name of the Run Storm Surge (m) Time % Differece

Time Difference

(hh:mm)

Imbudo (200307)

Observation 1.05 24/7/2003 2:27

Holland_JTWC 0.46 24/7/2003 3:00 -56.6% 00:33

Holland_HKO 0.57 25/7/2003 3:00 -45.3% 00:33

Young_JTWC 0.78 23/7/2003 20:00 -26.0% 06:27

Young_HKO 0.82 24/7/2003 3:00 -22.4% 00:33

Prapiroon (200606)

Observation 0.71 3/8/2006 08:47

Holland_JTWC 0.50 3/8/2006 2:00 -28.98% 06:47

Holland_HKO 0.50 3/8/2006 2:00 -29.22% 06:47

Young_JTWC 0.54 3/8/2006 2:00 -23.61% 06:47

Young_HKO 0.54 3/8/2006 2:00 -23.73% 06:47

Nuri (200812)

Observation 1.13 22/8/2008 16:17

Holland_JTWC 1.00 22/8/2008 14:00 -11.5% 02:17

Holland_HKO 1.64 22/8/2008 14:00 45.2% 02:17

Young_JTWC 0.76 22/8/2008 14:00 -33.0% 02:17

Young_HKO 1.16 22/8/2008 14:00 2.8% 02:17

Hagupit (200814)

Observation 1.77 23/9/2008 23:47

Holland_JTWC 1.71 23/9/2008 23:00 -3.4% 00:47

Holland_HKO 1.32 23/9/2008 23:00 -25.3% 00:47

Young_JTWC 3.09 23/9/2008 23:00 74.5% 00:47

Young_HKO 1.73 23/9/2008 20:00 -2.1% 03:47

TPK Station Storm Surge Results


32/41

31 Result and Discussion TBT Station

Tropical Cyclone

Name (ID) Name of the Run Storm Surge (m) Time % Differece

Time Difference

(hh:mm)

Imbudo (200307)

Observation 1.13 24/7/2003 7:22

Holland_JTWC 0.38 24/7/2003 7:00 -66.5% 00:22

Holland_HKO 0.74 24/7/2003 7:00 -34.4% 00:22

Young_JTWC 0.52 24/7/2003 11:00 -53.6% 03:38

Young_HKO 0.76 24/7/2003 7:00 -32.5% 00:22

Prapiroon (200606)

Observation 0.90 3/8/2006 19:05

Holland_JTWC 0.32 3/8/2006 13:00 -64.4% 06:05

Holland_HKO 0.41 3/8/2006 13:00 -54.1% 06:05

Young_JTWC 0.31 3/8/2006 13:00 -65.2% 06:05

Young_HKO 0.40 3/8/2006 13:00 -55.7% 06:05

Nuri (200812)

Observation 0.78 23/8/2008 0:00

Holland_JTWC 0.43 22/8/2008 21:00 -44.8% 03:00

Holland_HKO 0.52 23/8/2008 2:00 -33.9% 02:00

Young_JTWC 0.40 22/8/2008 21:00 -48.9% 03:00

Young_HKO 0.48 23/8/2008 2:00 -38.2% 02:00

Hagupit (200814)

Observation 1.46 24/9/2008 02:07

Holland_JTWC 1.33 24/9/2008 0:00 -8.6% 02:07

Holland_HKO 1.24 24/9/2008 4:00 -15.1% 01:53

Young_JTWC 2.37 24/9/2008 4:00 62.3% 01:53

Young_HKO 1.62 24/9/2008 5:00 10.9% 02:53

TBT Station Storm Surge Results


33/41

32

West Lamma Channel (WLC) Significant Wave Height Results

Result and Discussion WLC Station

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Hsig(m)

Obs Holland JTWC Holland HKO YOUNG JTWC YOUNG HKO

0

0.5

1

1.5

2

2.5

3

3.5

4

Hsig(m)

WLC Holland JTWC Holland HKO Young JTWC Young HKO

0

0.5

1

1.5

2

2.5

3

3.5

4

Hsig(m)

Obs Holland JTWC Holland HKO Young JTWC Young HKO

Typhoon Hagupit (200814) Typhoon Imbudo (200307)

Typhoon Nuri (200812)

0

0.5

1

1.5

2

2.5

3

3.5

Hsig(m)


Typhoon Prapiroon (200606)


34/41

33

West Lamma Channel (WLC) Result Comparison

Result and Discussion WLC Station

Tropical Cyclone

Name (ID)Name of the Run RMS Error % RMS Error

Imbudo (200307)

Holland_JTWC 0.77 26.72%

Holland_HKO 0.68 23.65%

Young_JTWC 0.54 18.54%

Young_HKO 0.56 19.49%

Prapiroon

(200606)




Young_HKO 0.39 17.56%

Nuri (200812)




Young_HKO 0.62 22.82%

Hagupit (200814)




Young_HKO 0.75 24.43%

Time Series Comparison


35/41

34 Result and Discussion WLC Station

Tropical Cyclone

Name (ID) Name of the Run Max Hsig (m) Time % Differece

Time Difference

(hh:mm)

Imbudo (200307)

Observation 3.38 24/7/2003 6:00

Holland_JTWC 2.15 23/7/2003 21:00 -36.4% +09:00

Holland_HKO 2.92 24/7/2003 3:00 -13.7% +03:00

Young_JTWC 2.95 24/7/2003 9:00 -12.6% -03:00

Young_HKO 3.24 24/7/2003 9:00 -4.1% -03:00

Prapiroon (200606)

Observation 2.99 3/8/2006 12:00

Holland_JTWC 1.52 3/8/2006 15:00 -49.2% -03:00

Holland_HKO 1.87 3/8/2006 15:00 -37.4% -03:00

Young_JTWC 2.12 3/8/2006 15:00 -29.0% -03:00

Young_HKO 2.28 3/8/2006 15:00 -23.6% -03:00

Nuri (200812)

Observation 3.11 22/8/2008 20:00

Holland_JTWC 3.12 22/8/2008 21:00 0.2% -01:00

Holland_HKO 3.46 22/8/2008 21:00 11.3% -01:00

Young_JTWC 2.37 22/8/2008 21:00 -23.8% -01:00

Young_HKO 3.48 22/8/2008 21:00 11.8% -01:00

Hagupit (200814)

Observation 3.49 24/9/2008 2:00

Holland_JTWC 3.63 23/9/2008 21:00 4.0% +05:00

Holland_HKO 3.45 24/9/2008 3:00 -1.2% -01:00

Young_JTWC 4.38 24/9/2008 3:00 25.4% -01:00

Young_HKO 3.88 24/9/2008 3:00 11.1% -01:00

West Lamma Channel (WLC) Result Comparison


36/41

35

Kau Yi Chau (KYC) Significant Wave Height Results

Result and Discussion KYC Station

0

0.5

1

1.5

2

2.5

3

3.5

4

Hsig(m)


0

0.5

1

1.5

2

2.5

3

Hsig(m)

KYC Holland JTWC Holland HKO Young JTWC Young HKO

0

0.5

1

1.5

2

2.5

Hsig(m)

Obs Holland JTWC Holland HKO Young JTWC Young HKO

0

0.5

1

1.5

2

2.5

3

Hsig(m)


Typhoon Hagupit (200814) Typhoon Imbudo (200307)

Typhoon Nuri (200812) Typhoon Prapiroon (200606)


37/41

36

Kau Yi Chau (KYC) Result Comparison

Result and Discussion KYC Station

Tropical Cyclone

Name (ID)Name of the Run RMS Error % RMS Error

Imbudo (200307)




Young_HKO 0.49 20.72%

Prapiroon

(200606)




Young_HKO 0.31 15.87%

Nuri (200812)




Young_HKO 0.49 26.51%

Hagupit (200814)




Young_HKO 0.59 20.87%

Time Series Comparison


38/41

37 Result and Discussion KYC Station

Tropical Cyclone

Name (ID) Name of the Run Max Hsig (m) Time % Differece

Time Difference

(hh:mm)

Imbudo (200307)

Observation 2.68 24/07/2003 07:00

Holland_JTWC 1.71 23/07/2003 21:00 -36.2% +10:00

Holland_HKO 2.22 24/07/2003 03:00 -17.1% +04:00

Young_JTWC 2.46 24/07/2003 09:00 -8.3% -02:00

Young_HKO 2.64 24/07/2003 09:00 -1.6% -02:00

Prapiroon (200606)

Observation 2.47 3/8/2006 11:00

Holland_JTWC 1.32 3/8/2006 15:00 -46.7% -04:00

Holland_HKO 1.61 3/8/2006 15:00 -34.8% -04:00

Young_JTWC 1.86 3/8/2006 15:00 -24.8% -04:00

Young_HKO 2.01 3/8/2006 15:00 -18.7% -04:00

Nuri (200812)

Observation 2.36 22/08/2008 20:00

Holland_JTWC 2.18 22/08/2008 21:00 -7.5% -01:00

Holland_HKO 2.17 22/08/2008 21:00 -8.0% -01:00

Young_JTWC 1.66 22/08/2008 21:00 -29.5% -01:00

Young_HKO 2.14 22/08/2008 21:00 -9.2% -01:00

Hagupit (200814)

Observation 3.31 24/09/2008 01:00

Holland_JTWC 2.88 23/09/2008 23:00 -12.9% +02:00

Holland_HKO 2.80 24/09/2008 03:00 -15.4% -02:00

Young_JTWC 3.43 23/09/2008 23:00 3.7% +02:00

Young_HKO 3.06 24/09/2008 03:00 -7.7% -02:00

Kau Yi Chau (KYC) Result Comparison

S f C i


39/41

38

Summary of Comparisons

Summary

Best Performance Model Results (Smallest % Error/ % RMS Error)

Max Storm Surge Max Hsig Time Series % RMS Error

Tropical Cyclone Name

(ID)QUB TPK TBT WLC KYC WLC KYC

Imbudo (200307) Young_HKO Young_HKO Young_HKO Young_HKO Young_HKO Young_JTWC Young_HKO

Prapiroon (200606) Young_HKO Young_JTWC Holland_HKO Young_HKO Young_HKO Young_HKO Young_HKO

Nuri (200812) Holland_HKO Young_HKO Holland_HKO Holland_JTWC Holland_JTWC Holland_JTWC Holland_JTWC

Hagupit (200814) Holland_JTWC Young_HKO Holland_JTWC Holland_HKO Young_JTWC Holland_HKO Holland_HKO

Best Typhoon Wind Model : Young

Best Best Track Data : HKO

C l i


40/41

39

Conclusion

1. For Hong Kong:

Best Typhoon Model : Young

Best Best Track Data: HKO

2. Storm surge results are always underestimated

3. Large time difference with the observed max data

Conclusion


41/41

40

EndThank you very much

14 johnny cheung

Documents