Building a fixed coastal observing and forecast system for Halifax Harbour

Transcription

1 Building a fixed coastal observing and forecast system for Halifax Harbour Jinyu Sheng 1 and Will Perrie 2 1 Department o Oceanography, Dalhousie University 2 Bedford InsEtute of Oceanography, DFO Research team: Wei Chen, Yi Sui, Fred Wolsyng Kyoko Ohashi, Pengcheng Wang Bash Toulany, Guoqiang Liu Yujuan Sun, Haibo Hu, Lanli Guo (MEOPAR Annual ScienEfic MeeEng, June 2014)

2 Principal Investigators and Collaborators for Initial Project 1.2a: Researchers InsEtuEons Research Areas Jinyu Sheng Dal Ocean circula1on modelling Will Perrie BIO/Dal Ocean wave modelling Ron Pelot Dal Risk assessment and analysis Keith Thompson Dal Ocean modelling and data assimila1on Hal Ritchie EC/Dal Atmospheric circula1on modelling Haibo Niu Dal Oil spill modelling Dave Hebert BIO/Dal Ocean observa1on (physical) Bill Li BIO/Dal Ocean observa1on (bio- chemical) Serge Desjardins EC/Dal Atmospheric circula1on modelling

3 Main objectives for Halifax Harbour Component: Develop a real-time forecast system for physical properties (sea level, currents, waves, temperature and salinity) within Halifax Harbour and the adjacent shelf. Develop schemes to assimilate physical observations (e.g., currents from mooring in Bedford Basin, surface currents from the high frequency radar on the inner shelf) into the model of Halifax Harbour and adjacent shelf. Demonstrate the capability for real-time forecasting of physical conditions in Halifax Harbour with quantified measures of forecast skill based on observations from moored instruments and high frequency radar measurements. Generate maps of the risk of ship collision taking into account forecast ocean conditions. Transition the real-time system to operations through a private sector partner.

4 Year 1: Timeline and Key Deliverables Reports on workshops with partners to coordinate planning, user needs, and communica1on of expected research results Deploy buoy in Halifax Harbour (working with the Observa1ons Core). Year 2: Deploy and test parallelized version of new wave model system based on WW3 and unstructured SWAN (Perrie). Organizing the 6 th Interna1onal Workshop on Modeling the Ocean (IWMO,

5 Year 3: Together with the Predic1on Core, evaluate analyses and predic1ons from the ini1al analysis and modelling system, and make results available to partners on a trial basis (Sheng, Perrie and Thompson). Year 4: Assessment of the benefit of assimila1on in terms of forecast skill, and comparison of results with those from exis1ng GEM- NEMO forecasts systems at coarser scale (Sheng and Perrie). Year 5: Publica1on of GEM- NEMO results and intercomparison with ini1al system(sheng, Perrie and Thompson).

6 1. Five- level nested- grid ocean circulaeon model

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10 2. Implementation of structured grid wave forecast system Large! Δx ~ 5km Δx ~ 25km Δx ~ 50m WW3 Δx ~ 1.3km SWAN (later) WAVEWATCHIII 2- way nested grids

11 48- hr Opera1onal Wave Forecasts h\p://extrememarine.ocean.dal.ca/dalcoast/wave_l1.php 2- way nested grids!

12 Test case - Hurricane Juan (2003) waves at 44258: Hs 9-10 m winds at 44258: 27.5 m/s sea eleva1on at 44258: 1.9m MSL 1.64m at Point Pleasant Park 12

13 DIA present model FBI new model difference DIA-FBI ~15% 13

14 Simulated Juan s peak intensity: Xu and Perrie 2013

15 Tests with unstructured SWAN AVE grid Point Pleasant Park after hurricane Juan SWAVE model Grid resolueon is 0.5km at coast to 70km in outer areas

16 Zoom to coastal area near Halifax at peak of storm SWAVE comparison with buoy 44258

17 Under extreme circumstances (hurricanes), up to 10% less momentum flux locally and advected away [Janssen 2012], especially for fast moving storms ReducEon of momentum flux to ocean can be up to 25% [Fan et al., 2010, JPO] With waves Without waves % magnitude of momentum flux into currents τ c rela1ve to the momentum flux from air, τ air, for experiments with (transi1on speed) TSP =5m/s and 10m/s. White dot is center of the storm. (c) (d) and (e)(f) are calculated by different drag coefficient.

18 Presently: update the fully coupled wave- current model for more accurate surface transport esemates (1) Old ROMS- SWAN model uses bulk parameter- based esemates of Stokes drif, which significantly underesemate Stokes drif compared to using wave spectrum. à Given the importance of Stokes drif in surface drif and wave- current interaceon, we expect that this updaeng can significantly improve simulaeons. (2) Update with new SWAN wave model, using newly developed dissipaeon and wind input terms à should improve the momentum flux between waves and currents.

19 A Prototype Ocean Circulation and Wave Forecast System for Halifax Harbour hgp://extrememarine.ocean.dal.ca/dalcoast MEOPAR HH Oil Spill Modeling & Response Workshop Halifax, NS Feb 4,

20 Summary and Future Work A prototype ocean prediction system for Halifax Harbour has been setup (extrememarine.ocean.dal.ca/dalcoast). The system predicts short-term forecasts of sea level, currents, temperature/salinity and ocean waves in the next 2 days. We will collaborate with Initial Project 1.1 to use their model results for the boundary conditions of the system. We will also collaborate with the Observation Core to validate the performance of the prediction system. We will make results available to partners on a trial basis. Observations (such as SST) will be assimilated into the prediction system. Wave-current interactions and effects of waves on the upper ocean currents and transports will be examined.