Deep-Water Oceanographic Buoys: Deployments, Measurements, Outcomes

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 Center Department of Hydraulic and Ocean Engineering National Cheng Kung University Tainan, Taiwan May 5-6, 2014 

2. Contents: • Backgrounds • Ocean Monitoring System in Taiwan • Applications of the Ocean Monitoring System • Deep-Water Buoy • Characteristics of Wind Sea and Swells • Conclusions

3. I. Backgrounds Weather, Oceans, and Tides around Taiwan Fig. 1 Weather system around Taiwan. Fig. 2 Tidal system around Taiwan.

4. Length of coastline Main island: 1139 km incl. small islands: 1600 km Eastern waters: Pacific Ocean ( d > 5000m) Seabed slope max. 1/10 rocky shoreline, cliff, beach Tidal diff. ~1.5m. max. Hs~20m Western waters: Taiwan Strait ( d < 200m) Seabed slope min. 1/1000 sandy beaches, dune, wetland Tidal diff. ~4.0m. max. Hs ~10m 150 km 400 km

5. II. 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)

6. Data Buoys 資料浮標 1. To collect marine & meteorological data in any water depth . 2. To be the basis of ocean monitoring. 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。 1997年取得第一型資料浮標專利 觀測項目 波浪海流水溫氣壓 風氣溫其他(水質…) Measurable items: -Wave • Current • Water temperature • Barometric pressure • Wind • Air temperature • Others, such as water quality Data Buoy Type I (patented in 1997)

7. 海上、海岸自動觀測站 Permanent Ocean & Coast Observing Systems 作為近海水文觀測之基礎 To be the basis of ocean monitoring 觀測項目 波浪潮汐海流水溫氣壓風氣溫雨量溼度日照其他 潮位站 Tide station Measurable items： • Wave, tide, and current • Water temperature • Barometric pressure • Wind and air temperature • Rain, humidity, and sunshine duration • Others 海上觀測樁 Ocean observation pile 海岸氣象站 Coastal weather station

8. 船用雷達 Vessel based radar 移動式 Vehicle based radar 岸基雷達 Land based radar 海況遙測技術 Remote Sensing Systems for Sea-State To collect marine data from an area of the sea surface by a more convenient way. 以非接觸之方式，蒐集表面區域的海象資料 觀測項目 波浪表面流 Measurable items: -Wave height -Wave period -Wave direction -Wave spectrum -Surface current Radar Images during Typhoon Nockten (Oct 24 22:00, 2004) 2004年那克坦颱風期間海面之雷達影像

9. Real-Time Data Transmission 即時資料傳輸 Half an hour after observation, users can access QC-d data. 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。 資料傳輸流程圖(data transmission) GSM / GPRS / Satellite 現場(Sites ) 使用者 (Clients) 資料品管 (Data QC) ADSL ADSL Relay station Radio Signal Internet Internet 00:30 01:30 02:30 . . . 23:30 00:00 01:00 02:00 . . . 23:00 觀測 分析 資料品管 資料傳輸 資料傳輸 Data transmission Data transmission observation analysis Data QC 30 25 10 13 20 分鐘(min)

10. III. Applications of the Ocean Monitoring System • During the typhoon period, COMC provides every 6 hours the following information to the government: • 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)

11. Tsunami warning on March 11, 2011 (Tohoku earthquake) http://www.jma.go.jp/jma/index.html

12. Tsunami Detection after the Japan Earthquake Occurred (astronomical)

13. IV. Deep-Water Buoys Tracks of typhoons approaching Taiwan from 1997 to 2006.

14. IV. Deep-Water Buoy • Where should we deploy the deep-water buoys? • 21o18’ N. , 124o03’ E.

15. CWB CWB CWB CWB CWB 300公里 近十年有超過67%於侵台之前通過台灣東方之海域 CWB CWB

16. 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

17. Data buoy 19 mm iron chain, 70 m Scope(mooring length/water depth) =1.25 38 mm nylon rope, 100 m 25 mm nylon rope, 3000 m 3 glass floats Water depth 5600 m 12 mm PE rope, 3000m 6 glass floats 19 mm iron chain,5 m Anchors 26 mm ironchain, 27.5 m 32 mm iron chain, 27.5 m Sea bed

18. Instruments Installed on the Data Buoy

19. Typhoon JELAWAT (Sep.27～28, 2012)

20. Significant wave heights and mean wave periods monitored by thePacific buoy

21. Wind speed and direction

22. Air pressure and temperature

23. Sea surface current

24. 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

25. 5.1 Selection of Wave Data Wind Speed and Direction 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).

26. 5.1 Selection of Wave Data Wind 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).

27. 5.2 Separation of Wind Sea and Swells 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.

28. 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),

29. 5.2 Separation of Wind Sea and Swells 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).

30. 5.2 Separation of Wind Sea and Swells Wave age, significant wave height, and mean wave period Fig. 5.4 Temporal variation in the significant wave height.

31. 5.2 Separation of Wind Sea and Swells Wave age, significant wave height, and mean wave period Fig. 5.5 Temporal variation in the mean wave period.

32. 5.2 Separation of Wind Sea and Swells 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)

33. 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 :

34. 5.3 Propagation of Swells Swells produced by Malakas Typhoon Fig. 5.6 Track of Malakas Typhoon (2010/09/21 - 2010/9/26).

35. 5.3 Propagation of Swells 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.

36. 5.3 Propagation of Swells 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).

37. 5.3 Propagation of Swells 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).

38. 5.4 Generation and Disappearance of Swells 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.

39. 5.4 Generation and Disappearance of Swells Disappearance of swells: The weather map (Fig. 5.9) shows that the Malakas Typhoon landed Japan on 2010/09/26/02 (Taiwan Time). The distance, , from the Malakas Typhoon to the deep-water 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(Taiwan Time). Consistent with the results shown in Fig. 5.3.

40. 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).

41. 5.5 Characteristics of Wind Sea and Swells Fully-developed Wind Sea (2/4) Fig. 5.11 Comparison of the measured wave spectrumat 2010/09/27/06:00 with the PM spectrum (First Time Zone). Fig. 5.12 Comparison of the measured wave spectrumat 2010/09/28/08:00 with the PM spectrum(Second Time Zone).

42. 5.5 Characteristics of Wind Sea and Swells Fully-developed Wind Sea (3/4) Fig. 5.13 Comparison of the measured wave spectrumat 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).

43. 5.5 Characteristics of Wind Sea and Swells Fully-developed Wind Sea (4/4) Fig. 5.15 Comparison of the measured wave spectrum at 2010/09/30/22:00with the PM spectrum (Third Time Zone, Part III).

44. 5.5 Characteristics of Wind Sea and Swells 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)

45. 5.5 Characteristics of Wind Sea and Swells Characteristics of Swells (2/11) Fig. 5.17 Weather map around eastern water of Taiwan on July14, 2011(14:00, Taiwan Time).

46. 5.5 Characteristics of Wind Sea and Swells Characteristics of Swells (3/11) Fig. 5.18 Weather map around eastern water of Taiwan on July19, 2011 (20:00, Taiwan Time).

47. 5.5 Characteristics of Wind Sea and Swells Characteristics of Swells (4/11) Apparent swell appears from 2011/7/16/16:00 (16th Hour) to 2011/7/18/12:00 (60th Hour). Fig. 5.19 Evolution of peak period of the swell and wind speed measuredby the deep-water buoy from July 16, 00:00, 2011 to July 19, 00:00 (Taiwan Time).

48. 5.5 Characteristics of Wind Sea and Swells Characteristics of Swells (5/11) Fig. 5.20 Directional wave spectrum obtained from the deep-water buoydeployed at Western North Pacific on 2011/07/16/23:00 (Taiwan Time).

49. 5.5 Characteristics of Wind Sea and Swells Characteristics of Swells (6/11) Three Time Zones: Zone I: 2011/07/15/00:00 - 2011/07/16/15:00 Zone II: 2011/07/16/00:00 - 2011/07/18/12:00 Zone III: 2011/07/18/13:00 - 2011/07/19/23:00 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).

50. 5.5 Characteristics of Wind Sea and Swells Characteristics of Swells (7/11) Fig. 5.22Temporal evolution of the wave spectraduring the period of Ma-OnTyphoonat Time Zone I(from 2011/07/15/00:00 to2011/07/19/23:00, Taiwan Time). Fig. 5.23Temporal evolution of the wave spectraduring the period of Ma-On Typhoon atTime Zone II (from 2011/07/16/00:00 to2011/07/18/12:00, Taiwan Time).