WaMoS II Wave Monitoring System

Transcription

1 WaMoS II Wave Monitoring System - An application of WaMoS II at Duck - Katrin Hessner, K. Reichert, J. Dannenberg OceanWaveS GmbH, Germany Kent Hathaway, Don Resio Engineering Research Development Center Us Army Corps of Engineers, USA 9 th INTERNATIONAL WORKSHOP ON WAVE HINDCASTING AND FORECASTING VICTORIA, B.C., CANADA, September 24-29, 26

2 Outline WaMoS II Installation at Duck Statistical wave parameters Sea surface elevation maps Summary and Outlook

3 Components of WaMoS II and applications

4 X-Band Radar image: Sea clutter

5 WaMoS II radar images from the Dutch coast: Time series of 'sea clutter' image with directional unambiguity Corresponding frequency-direction spectrum

6 Standard WaMoS II Output Parameters 2-dimensional frequency direction spectrum 2-dimensional wave number spectrum -dimensional spectrum - mean direction - spread Wave length peak swell wind sea Wave direction peak swell wind sea Wave period peak swell wind sea Significant wave height total swell wind sea Surface current speed and direction Type approved for accuracy by DNV and GL: Significant wave height +/- % (max. +/-.5 m) Wave period +/-.5 s Wave direction +/- 2 Wave length +/- %

7 WaMoS II User Interface Individual configuration Directional Wave Spectrum Average Surface Curren Vector -D Frequency Spectrum Swell and wind sea syste Radar Image Time Series of Hs and Tp

8 USACE Field Research Facility at Duck, North Carolina, USA From February to October 25. Atlantic Ocean USA radar antenna pier anemometer pressure gauge N WaMoS II analyis areas Wave Rider no radar return max km

9 USACE Field Research Facility at Duck, North Carolina, USA Directly measured sea state parameter: Peak wave period (Tp) Peak wave direction (θp) Wave Period 2 T [s] 5 5 OceanWaveS GmbH Wave Direction (coming from) 8 θ [ ] OceanWaveS GmbH 26 S E 5 WaMoS II: peak wave swell wind Sea Time [Days of Sep., 25] too low radar return Wave Rider: peak wave 3 N

10 USACE Field Research Facility at Duck, North Carolina, USA Directly measured sea state parameter: Peak wave period (Tp) Peak wave direction (θp) Wave Period 2 T [s] 5 5 OceanWaveS GmbH Wave Direction (coming from) 8 θ [ ] OceanWaveS GmbH 26 S E 5 WaMoS II: peak wave swell wind Sea Time [Days of Sep., 25] too low radar return Wave Rider: peak wave 3 N

11 USACE Field Research Facility at Duck, North Carolina, USA Indirectly measured sea state parameter: Wind at the pier Significant wave height (Hs) Hs [m] W [m/s] θ W [ ] too low radar backscatter offshore wind onshore wind Significant Wave Height Wind Speed Wind Direction (coming from) WaMoS II th 8, 2:4 UTC th 9, : UTC Wave Rider OceanWaveS GmbH OceanWaveS GmbH Time [Days of Sep., 25] OceanWaveS GmbH N W S E N

12 USACE Field Research Facility at Duck, North Carolina, USA Correlation between Hs variation and wind Hs (WaMoS II)- Hs (Wave Rider) onshore wind wind direction offshore wind low wind speed -. moderate wind speed (N) 9(E) 8(S) 27(W)36(N) θ w [ ] 2.5 % of data points ( N =298) Hs (WaMoS II)- Hs (Wave Rider) low wind speed moderate - high onshore wind -.5 offshore wind W [m/s] 2.5 % of data points ( N =298)

13 Radar imaging mechanism Off-shore wind condition N Sep. 8, 25 2:4:UTC off-shore wind N On-shore wind condition Sep. 9, 25 ::UTC on-shore wind speed = 3 m/s direction = 223 speed = 5 m/s direction = 54 km Hs: WaMoS II :.5m Wave Rider:.55m OceanWaveS GmbH (25) radar return no max km Hs: WaMoS II :.2m Wave Rider:.49 m OceanWaveS GmbH (25) radar return no max radar look down wind Wind parasitic capillary (white crest) waves radar look up wind Wind parasitic capillary (white crest) waves wave propagation wave propagation

14 USACE Field Research Facility at Duck, North Carolina, USA Correlation between Hs variation and wind 4 3 WaMoS II: Hs wind corrected: Hs* significant wave height Wave Rider: Hs Hs [m] Time [Days of Sep., 25] % of data points 5 Hs(WaMoS II) [m] 3 2 r =.8 RMS =.5 m biaz =.25 m Hs(Wave Rider) [m] % of data pointes ( N =3582) Hs* (WaMoS II) [m] 3 2 r =.92 RMS =.26 m biaz =.5 m Hs(Wave Rider) [m] % of data pointes ( N =3582) 4 3 2

15 Inversion Scheme (Nieto et al., 24) Radar Images Sea Surface Elevation Maps t = t Radar t = t t = 2 t G( r, t) t = 2 t t = 3 t FFT A I( k,ω ), Φ( k, ω) t = 3 t Disperstion Relation ω (k) MTF A w( k,ω ), Φ( k, ω)... t = N t FFT Σ A( k, ω ) cos( kr+ ω t+ Φ( k, ω )) ζ( r,) t i i i i i i... t = N t

16 Radar Backscatter Image Duck, Sep. 6, 25, 6:3 UTC Hs Tp θp WaMoS II: 2.5m 9.9s 7 Wave Rider: 2.66m 8.5s 73 Pressure gage: 2.66m 8.2s 78

17 Sea surface elevation map Duck, Sep. 6, 25, 6:3 UTC Hs Tp θp WaMoS II: 2.5m 9.9s 7 Wave Rider: 2.66m 8.5s 73 Pressure gage: 2.66m 8.2s 78

18 USACE Field Research Facility at Duck, North Carolina, USA N X-Band Radar image WaMoS II : Hs = 2.5 m Tp= 9.9 s θp = 8 Hs :3:UTC Wind 2m/s N Sea surface elevation pressure gage Surface elevation map :3:UTC Wind 2m/s Buoy: Hs = 2.7 m Tp= 8.5 s θp = 73 km OceanWaveS GmbH radar return no max km surface elevation -2.5m 2.5m OceanWaveS GmbH

19 USACE Field Research Facility at Duck, North Carolina, USA WaMoS II: Sea surface elevation Sep. 6, 25, 6:3 UTC at the estimated position of the pressure gage η [m] temporal transect dt = RPT = 2.65s dt =.5 s OceanwaveS GmbH Time [s] η [m] spatial transect in wave propagation direction propagation direction ds = 7.5 m OceanwaveS GmbH Distance [m]

20 Sea surface elevation comparison Sea surface elevation at the estimated position of the pressure gauge WaMoS II : red Pressure gage(id ): blue η [m] WaMoS II WaMoS II : :3: UTC Pressure gage : :5:5 UTC Pressure gage (Id ) OceanwaveS GmbH Time [s] - No exact location of the pressure gauge relativ to the radar antenna - No time sychronisation between the two sensors Hs 4 standard deviation of the surface elevation Hs =.87 m (pressure gage ) Hs = 2.66 m (total pressure gage 3)

21 Conclusions and outlook WaMoS II delivers directional wave spectra and current parameters in real time on an operational basis Directly measured wave data (peak wave period and direction) are in good agreement with reference data Due to coastal effects at Duck, the indirect measured wave parameter significant wave height is effected by the local wind The wind effect can be corrected, therefore independent wind measurements are recommended for specific coastal WaMoS II installations like at Duck Validation of wind correction algorithm Duck Other coastal installations Validation of WaMoS II sea surface elevation Collocation of WaMoS II and pressure gage data