copyright 2009 coastal ocean monitoring center. all right reserved. 0 deep-water oceanographic...

Copyright 2009 Coastal Ocean Monitoring Center. All right reserved.

http://www.comc.ncku.edu.tw 1

Deep-Water Oceanographic Buoys:Deployments, Measurements, Outcomes

Wind Sea and Swells Characteristics Derived from the Deep-Water Buoy at Western North

Pacific

Ching-Jer Huang

Coastal Ocean Monitoring CenterDepartment of Hydraulic and Ocean Engineering

National Cheng Kung UniversityTainan, Taiwan

May 5-6, 2014



Contents:

I. Backgrounds

II. Ocean Monitoring System in Taiwan

III. Applications of the Ocean Monitoring System

IV. Deep-Water Buoy

V. Characteristics of Wind Sea and Swells

VI. Conclusions



I. I. Backgrounds Backgrounds

Weather, Oceans, and Tides around Taiwan

Fig. 2 Tidal system around Taiwan.

Fig. 1 Weather system around Taiwan.



Length of coastline Main island: 1139 kmincl. small islands: 1600 km

Eastern waters:Pacific Ocean ( d > 5000 m)Seabed slope max. 1/10rocky shoreline, cliff, beachTidal diff. ~1.5 m. max. Hs~20 m

Western waters:Taiwan Strait ( d < 200 m)Seabed slope min. 1/1000sandy beaches, dune, wetlandTidal diff. ~4.0 m. max. Hs ~10 m

400 km

150 km



II. Ocean Monitoring System in TaiwanII. Ocean Monitoring System in Taiwan

COMC focuses on developing automated meteo-oceanographic measurement systems, supported mainly by Water Resources Agency (WRA) and Central Weather Bureau (CWB).

Coastal Ocean Monitoring Center (COMC),National Cheng Kung University (NCKU)



觀測項目1997年取得第一型資料浮標專利

Data Buoys

Data Buoy Type I (patented in 1997)

1.於淺水及深水區蒐集海氣象資料。2.作為近海水文觀測之基礎。

1. To collect marine & meteorological data in any

water depth .2. To be the basis of ocean monitoring.

Measurable items:

-Wave

-Current

-Water temperature

-Barometric pressure

-Wind

-Air temperature

-Others, such as water quality

波浪海流水溫氣壓風氣溫其他 ( 水質… )



觀測項目

Permanent Ocean & Coast Observing Permanent Ocean & Coast Observing SystemsSystems

海岸氣象站Coastal weather station

潮位站Tide station

海上觀測樁Ocean observation pile

波浪潮汐海流水溫氣壓風氣溫雨量溼度日照其他

Measurable items ：-Wave, tide, and current

-Water temperature

-Barometric pressure

-Wind and air temperature

-Rain, humidity, and sunshine duration

-Others

作為近海水文觀測之基礎 To be the basis of ocean monitoring



Radar Images duringTyphoon Nockten

(Oct 24 22:00, 2004)

Measurable items:-Wave height-Wave period-Wave direction-Wave spectrum-Surface current

岸基雷達Land based radarLand based radar

Remote Sensing Systems for Sea-StateRemote Sensing Systems for Sea-State

移動式Vehicle based radarVehicle based radar

船用雷達Vessel based radarVessel based radar

波浪表面流觀測項目

以非接觸之方式，蒐集表面區域的海象資料

To collect marine data from an area of the sea surface by a more convenient way.

2004年那克坦颱風期間海面之雷達影像



00:0001:0002:00

.

.

.23:00

00:3001:3002:30

.

.

.23:30

Radio Radio Signal Signal

GSM / GPRS / SatelliteGSM / GPRS / Satellite現場 ((SitesSites ) )

資料品管((Data QC)Data QC)

使用者((Clients)Clients)

RelayRelaystationstation

ADSLADSL

InternetInternet

Real-Time Data TransmissionReal-Time Data Transmission於觀測結束約半小時後，使用者可取得通過品管檢測之資料。

Half an hour after observation, users can access QC-d data.

資料傳輸流程圖 (data transmission)

ADSLADSL

InternetInternet

分鐘 (min)10

observation analysisData

transmission

13 20

Data QCData

transmission

25 30

觀測分析資料傳輸資料品管資料傳輸



III. Applications of the Ocean Monitoring System

During the typhoon period, COMC provides every 6 hours the

following information to the government:

(i)Forecasting water level at main river mouths

(ii) Forecasting of high water levels and arrival times around

Taiwan in 3 days

(iii) Present sea states around Taiwan (based on the data obtained

from buoys)

(iv) Wave height of swells around the coastal area of Taiwan

(v) Run-up and overtopping around some selected seawalls (with

high disaster potential)



http://www.jma.go.jp/jma/index.html

Tsunami warning on March 11, 2011 (Tohoku earthquake)



(astronomical)

Tsunami Detection after the Japan Earthquake Occurred



Tracks of typhoons approaching Taiwan from 1997 to 2006.

IV. Deep-Water Buoys



Where should we deploy the deep-water buoys?

21o18’ N. , 124o03’ E.

IV. Deep-Water Buoy



近十年有超過 67%於侵台之前通過台灣東方之海域

CWB

CWB

CWB

CWB

CWB

CWB

CWB

300公里



台東外洋資料浮標台東東南邊約 300公里水深達 5610公尺東經 123 度 59 分 54秒北緯 21 度 43 分 36秒

風速、風向波高、週期、波向氣壓、氣溫、水溫流速、流向



25 mm nylon rope, 3000 m

Data buoy

19 mm iron chain, 70 m

38 mm nylon rope, 100 m

12 mm PE rope, 3000m

Water depth 5600 m

Sea bed

Anchors

Scope (mooring length/water depth) =1.25

3 glass floats

32 mm iron chain, 27.5 m

19 mm iron chain, 5 m

26 mm iron chain,27.5 m

6 glass floats



Instruments Installed on the Data Buoy



Typhoon JELAWAT (Sep.27 ～ 28, 2012)



Significant wave heights and mean wave periods monitored by the Pacific buoy

9/28 0時 18.88m

9/28 0時 11.6s



Wind speed and direction9/27 23時，陣風41.6m/s

平均風30.4m/s



Air pressure and temperature

9/28 03時 934.9hPa

9/28 04時，氣溫23.6℃水溫23.5℃



Sea surface current9/28 16時 114.2cm/s



V. Characteristics of Wind Sea and Swells

5.1 Selection of wave data

5.2 Separation of wind sea and swells

5.3 Propagation of swells

5.4 Generation and disappearance of swells

5.5 Characteristics of wind sea and swells



5.1 Selection of Wave Data

Fig. 5.1 Temporal variations in the wind speed at 10 m high from 2010/09/26/12:00 to 2010/09/30/23:00 (Taiwan Time).

Wind Speed and Direction



5.1 Selection of Wave DataWind Speed and Direction

Fig. 5.2 Temporal variations in the wind direction at 3 m high from 2010/09/26/12:00 to 2010/09/30/23:00 (Taiwan Time).



A wind wave system which is directly generated and

affected by local winds is called a wind sea.

A swell consists of wind-generated waves that are not

generated by the local wind at that time. They have been

generated elsewhere some time ago.

5.2 Separation of Wind Sea and Swells



Separation of Wind Sea and Swell is based on the wave age (Ag),

which is defined as

: phase velocity of the peak-frequency wave

: wind speed at an elevation of 10 m

: Wind waves (wind sea)

: Swell

Fully-developed Swells:

Mitsuyasu (1981),

Donelan et al. (1993),


10U

CA p

g

pC

10U

1gA

1gA

4.1gA

29.1gA




Wave age, significant wave height, and mean wave period

Fig. 5.3 Temporal variation in the wave age for the waves measured by the deep-water buoy from 2010/09/26/12:00 to 2010/09/30/23:00 (Taiwan Time).





Fig. 5.4 Temporal variation in the significant wave height.





Fig. 5.5 Temporal variation in the mean wave period.




Based on the values of wave age, the waves appear at various times

can be categorized into three Time Zones:

Time Zone I : 2010/09/26/12:00 - 2010/09/27/20:00 (32 hours)

wave age: 2.5 - 3.8, =1.70 - 2.39 m, = 8.0 - 9.3 s

(Swells dominate)

Time Zone II : 2010/09/27/20:00 - 2010/09/28/20:00 (24 hours)

wave age: 1.7 - 2.5, =1.30 - 1.80 m, = 6.1 - 8.0 s

(Swells decrease and wind sea increases)

Time Zone III : 2010/09/28/20:00 - 2010/09/30/23:00 (51 hours)

wave age: 1.3 - 2.2, =1.20 - 1.46 m, = 5.0 - 6.2 s

(Wind sea dominates)

SH meanT

SH meanT

SH meanT



5.3 Propagation of Swells

Dispersion relationship for linear water waves:

g : gravitational acceleration, k : wave number, h : water depth

Shallow-water waves ( ):

Deep-water waves ( ):

c : phase velocity of waves, T : wave period

Group velocity

In shallow water :

In deep water :

)(tanh2 khgk

10/kh

kh Tg

c 2

ghc

)2sinh

21(

2 kh

khc

dk

dcg

ccg

Tg

ccg

4

5.0




Swells produced by Malakas Typhoon

Fig. 5.6 Track of Malakas Typhoon (2010/09/21 - 2010/9/26).



Fig. 5.7 Weather map around the deep-water buoy deployed at Western North Pacific on 2010/09/24/14:00 (Taiwan Time). Taiwan Time - 8 hours = UTC time.





10092612

0.1

0.2

0.3

0.4

0

30

60

90

120

150

180

210

240

270

300

330

0.0859Hz主頻

78.75主波向

m2/Hz

74平均風向 1

1.5

2

2.5

3

3.5

4

4.5

5

5.5

Fig. 5.8 Directional wave spectrum obtained from the deep-water buoy deployed at Western North Pacific on 2010/09/26/20:00 (Taiwan Time).




Fig. 5.9 Weather map around the deep-water buoy deployed at Western North Pacific on 2010/09/25/18:00 (UTC Time), 2010/09/26/02:00 (Taiwan Time).



Generation and detection of swells:

From Fig. 5.7, the distance, , from the Malakas Typhoon to the deep-water buoy

is approximately 1165 km.

From Fig. 5.5, the mean wave period in Time Zone I is

The produced swell will take about 46 hours to reach the deep-water buoy.

2010/9/24/14:00 (Taiwan Time, Fig. 5.7) + 46 Hrs = 2010/09/26/12:00 (Taiwan Time)

Consistent with the results shown in Fig. 5.3.

5.4 Generation and Disappearance of Swells

PR

sTZ

0.9

smTg

cg

/025.74

hrsc

Rt

g

P 06.46



5.4 Generation and Disappearance of Swells

Disappearance of swells:

The weather map (Fig. 5.9) shows that the Malakas Typhoon landed Japan on 2010/0

9/26/02 (Taiwan Time). The distance, , from the Malakas Typhoon to the deep-wa

ter buoy is approximately 1800 km.

From Fig. 5.5, the mean wave period in Time Zone III is

This effect will be detected by the deep-water buoy 80 hours later.

2010/09/26/02:00 (Taiwan Time, Fig. 5.9) + ８０ Hrs = 2010/ ２９／１０：００ (Ta

iwan Time). Consistent with the results shown in Fig. 5.3.

PR

sTZ ８．０

smTg

cg /4

６．２５

hrsc

Rt

g

P ８０



5.5 Characteristics of Wind Sea and Swells

Fully-developed Wind Sea (1/4)

Fig. 5.10 Variations in the wave spectrum measured by the deep-water buoy deployed at the Western North pacific from 2010/09/27/06:00 to 2010/09/30/22:00 Taiwan Time).





0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50

1

2

3

4

5

6

7

Frequency, f (Hz)

Spe

ctra

l Den

sity

, S(f

) (m

2/H

z)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50

1

2

3

4

5

6

7

Frequency, f (Hz)

Spe

ctra

l Den

sity

, S(f

) (m

2/H

z)

Fig. 5.11 Comparison of the measured wave spectrum at 2010/09/27/06:00 with the PM spectrum (First Time Zone).

Fig. 5.12 Comparison of the measured wave spectrum at 2010/09/28/08:00 with the PM spectrum (Second Time Zone).





0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.40

1

2

3

4

5

6

7

Frequency, f (Hz)

Spe

ctra

l Den

sity

, S

(f)

(m2 /

Hz)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.40

1

2

3

4

5

6

7

Frequency, f (Hz)

Spe

ctra

l Den

sity

, S

(f)

(m2 /

Hz)

Fig. 5.13 Comparison of the measured wave spectrum at 2010/09/30/14:00 with the PM spectrum (Third Time Zone, Part I).

Fig. 5.14 Comparison of the measured wave spectrum at 2010/09/30/21:00 with the PM spectrum (Third Time Zone, Part II).



0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.40

1

2

3

4

5

6

7

Frequency, f (Hz)

Spe

ctra

l Den

sity

, S

(f)

(m2 /

Hz)



Fig. 5.15 Comparison of the measured wave spectrum at 2010/09/30/22:00 with the PM spectrum (Third Time Zone, Part III).




Characteristics of Swells (1/11)

Swells produced by Ma-On Typhoon (July 12-20, 2011)

Fig. 5.16 Track of Ma-On Typhoon (July 12-31, 2011)



5.5 Characteristics of Wind Sea and SwellsCharacteristics of Swells (2/11)

Fig. 5.17 Weather map around eastern water of Taiwan on July14, 2011 (14:00, Taiwan Time).




Fig. 5.18 Weather map around eastern water of Taiwan on July19, 2011 (20:00, Taiwan Time).



0 10 20 30 40 50 60 70 800

5

10

15

20

Time (hr)

P

eak

Per

iod,

Tp

(s)

0 10 20 30 40 50 60 70 800

10

20

30

40

Win

d S

peed

,

U1

0 (

m/s

)

U10

Tp


Fig. 5.19 Evolution of peak period of the swell and wind speed measured by the deep-water buoy from July 16, 00:00, 2011 to July 19, 00:00 (Taiwan Time).

Apparent swell appears from 2011/7/16/16:00 (16th Hour) to 2011/7/18/12:00 (60th Hour).

sTp 14



11071623

0.1

0.2

0.3

0.4

0

30

60

90

120

150

180

210

240

270

300

330

0.0762Hz主頻

90主波向

m2/Hz

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6


Fig. 5.20 Directional wave spectrum obtained from the deep-water buoy deployed at Western North Pacific on 2011/07/16/23:00 (Taiwan Time).




Fig. 5.21 Temporal evolution of the wave spectra during the period of Ma-On Typhoon from 2011/07/15/00:00 to 2011/07/19/ 23:00 (Taiwan Time).

Three Time Zones:

Zone I : 2011/07/15/00:00 - 2011/07/16/15:00Zone II : 2011/07/16/00:00 - 2011/07/18/12:00Zone III: 2011/07/18/13:00 - 2011/07/19/23:00




Fig. 5.22 Temporal evolution of the wave spectra during the period of Ma-On Typhoon at

Time Zone I (from 2011/07/15/00:00 to 2011/07/19/23:00, Taiwan Time).

Fig. 5.23 Temporal evolution of the wave spectra during the period of Ma-On Typhoon at Time Zone II (from 2011/07/16/00:00 to 2011/07/18/12:00, Taiwan Time).



10-2

10-1

100

10-4

10-3

10-2

10-1

100

101

102

Frequency, f (Hz)

Spe

ctra

l Den

sity

, S

(f)

(m2 /

Hz)

Zone IZone IIZone III


Fig. 5.24 Temporal evolution of the wave spectra during the period of Ma-On Typhoon at Time Zone II (from 2011/07/18/13:00 to 2011/07/19/23:00,

Taiwan Time).

Fig. 5.25 Representative wave spectra obtained by the deep-water buoy deployed at Western North Pacific during the period of Ma-On Typhoon from 2011/07/15/00:00 to 2011/07/17/ 23:00 (Taiwan Time).




Pierson-Moskowitz (P-M) Spectrum (1964)

245

001995.0exp

0005.0)(

sHfffS

Modified JONSWAP Spectrum (Goda, 1999)

22 21exp4542 )(4

5exp)(

pff

ppsj fTfTHfS

)ln(01915.0094.1)9.1(185.00336.023.0

06238.01

j

569.0)5.2(532.01

T

Tp

: frequency, : peak frequency, : significant wave height

: spectral width parameter, T: mean wave period, and : peak enhancement factor

f pf SH




Modified Wallops Spectrum (Huang et al., 1981; Goda, 1999)

412 )(

4exp)( fT

mfTHfS pmm

psw

057.1

4)5(

4)1(

)2(7458.014/)1(4

0624.0

mm

mm

m

w

072.1)5.0(259.11

m

TTp

f sHpT

T

: frequency, : peak frequency, : significant wave height

: mean wave period, and : peak enhancement factor




Fig. 5.26 Comparison of measured wave spectrum at Time Zone II with the modified Wallop Spectrum.

Fig. 5.27 Comparison of measured wave spectrum at Time Zone II with the modified JONSWAP Spectrum

.

Comparison of measured wave spectrum at Time Zone II with the modified Wallop Spectrum and the modified JONSWAP spectrum.



VI. Conclusions

1. Data buoys are very important platforms for installing various sensors to

monitor the sea states, such as wind speed, wind direction, wave height, wave

direction, currents, etc.

2. The real-time information obtained from the buoys is important for rapid and

effective responses to possible disasters.

3. The deployment of deep-water buoys is a hard task, but the obtained data

provide much earlier precious information for handling possible disasters.



Thank you! Comments are mostly welcome.

copyright 2009 coastal ocean monitoring center. all right reserved. 0 deep-water oceanographic...

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