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  1. 1. Jie Liu EOSC 571 Term2 Evaluation of NEMO model on Fraser River plume in the Strait of Georgia
  2. 2. Contents 1. Motivation 2. Main task 3. Research Questions 4. Methods 5. Research plan
  3. 3. Motivation Strait of Georgia and Salish Sea are home to a large population of residence in BC. Many activities in the Fraser River estuary are affected by salinity intrusions. Motions of Fraser River plumes influence pollutant dispersal, sedimentation and nutrient. On-going need to assess the impact in coastal communities(NASA)
  4. 4. Main task N (Soontiens et al, 2015) NEMO Model in regional configuration 398 * 898 * 40 gird cells 150 rivers parameterized Produce nowcasts and forecasts
  5. 5. Main task (http://nbviewer.ipython.org/urls/bitbucket.org/salishsea/analysis/ra w/tip/Idalia/Drifters_Ariane_Comparison.ipynb) Drifters: Released near the Fraser mouth last September
  6. 6. Research Questions Aim: Test and evaluate river treatments for Fraser River as well as other external forcing factors, such as tide and wind, to acquire more accurate plume properties in nowcast and forecast model results and better simulate surface currents in the Fraser River plume. 2 In which way should I add river treatment into the NEMO model domain and what physical factors should be taken into account? How do river discharge, tide and wind affect plume properties, such as salinity? How do plume properties vary spatially and in short and long time scales? What model skill should I use to evaluate Fraser River plume from NEMO model results in Salish Sea domain?
  7. 7. Methods River treatment in the model Prolong the length, broaden the width and deepen the depth of river channel in model domain. Straight or curved river channel? Up to where? Mission, Hope or somewhere else? Perform hindcast for last September Boundary conditions: 1) no tidal energy gets to the eastern edge of river channel. 2) steady-state river discharge at points outside the tidal influence.(Google map) Sensitivity experiments of lengths
  8. 8. Methods River discharge at river mouth Currently: using data from Environment Canada gauge at Hope. Alard & Anne s estimate of discharge at Chilliwack: Q = Marks estimate of discharge at Fraser River mouth = My estimate of discharge at Fraser River mouth: Q = QQQ ChehalisHarrisonH ba +++ ope 500012.1 +QHope Does not experience tidal fluctuations Not accurate enough to estimate discharge at river mouth QQQ PittHarrisonH ++ ope QPortMann
  9. 9. Methods Assessment of river discharge and tide in the estuary and near-field plume area Stratification and position of salt wedge R.A.Kostaschuk & L.A.Atwood develop a multiple regression model to predict Fraser River salt wedge position. M.J.Halverson & R.Pawlowicz derive a conceptual model for the combined effect on the Fraser River plume salinity. P.MacCready estimates the importance of tide induced mixing with tidally averaged, volume integrated mechanism energy budget in ROMS. Hindcast is needed to perform: a) Select several stations, such as New Westminster, Mission and Hope b) Simulation with all the forcing conditions, including tides and atmospheric forcing. c) Simulation with all the forcing except tide. d) Simulation with all the forcing but only tuning several constitutes of tide. https://www.google.com/search?newwindo
  10. 10. Methods Assessment of wind in the far-field plume area Perform hincasts from period last year or this year: a) Simulation with strong local wind and flood tide b) Simulation with weak local wind and flood tide c) Simulation with strong local wind and ebb tide d) Simulation with weak local wind and ebb tide. May need sensitivity experiment on Turbulence Closures a) Generic Length Scale(GLS[Madec et al, 2012]) calculate vertical mixing and turbulence b) Large-McWilliams-Doney(LMD[Large et al, 1994]) been added in
  11. 11. Methods Surface salinity comparisons with ferry observations 3 Data: Daily surface salinity from Queen of Alberni, VENUS(ONC). Four round trip per day. Complete transect takes about 2hr.
  12. 12. Methods Surface salinity comparisons with ferry observations Analysis: a)Comparisons of daily surface salinity plots allow to see the features of variation and difference between observation. b) Comparisons in different time period since last September is feasible to excavate short and long time scales of plume salinity variation.
  13. 13. Methods Evaluation of model skills Skill Score(SS) for sensitivity experiment in estuary, near- and far-field plume: SS = 1-MSE/MSER Where MSE = < > SS > 0 improvement SS < 0 worse SS = 1 perfect ( )om 2 Willmott Skill(Willmott[1981]) for model skill(different physical variables) ( )ooo MSE WS + = m 2 1
  14. 14. Solutions wrap-up In which way should I add river treatment into the NEMO model domain and what physical factors should be taken into account? River treatment in the model How do river discharge, tide and wind affect plume properties, such as salinity? Assessment of river discharge, tide and wind in the whole estuary-plume system How do plume properties vary spatially and in short and long time scales? Salinity comparisons with ferry observations and CTD observations What model skill should I use to evaluate Fraser River plume from NEMO model results in Salish Sea domain? Evaluation of model skill
  15. 15. Research plan Start: Compare surface salinity with observations(last Sep up to now and future) Compare surface currents with drifters(last Sep, Oct) Add river treatment into model Sensitivity test of paramaters SS Simulation with all the forcing Simulation with all the forcing except tide Simulation with all the forcing with only several tidal constituents Simulation with strong wind, flood tide Simulation with strong wind, ebb tide Simulation with weak wind, strong tide Simulation with weak wind, ebb tide WS Improve nowcast and forecats Perform hincast
  16. 16. Reference Lebeaupin Brossier C, Branger K, Drobinski P. Sensitivity of the northwestern Mediterranean Sea coastal and thermohaline circulations simulated by the 1/12-resolution ocean model NEMO-MED12 to the spatial and temporal resolution of atmospheric forcing[J]. Ocean Modelling, 2012, 43: 94-107.2 Stronach J A. The Fraser River plume, Strait of Georgia[J]. Ocean Management, 1981, 6(2): 201-221.2 Hetland R D. Relating river plume structure to vertical mixing[J]. Journal of Physical Oceanography, 2005, 35(9): 1667-1688.3 Hetland R D, MacDonald D G. Spreading in the near-field Merrimack River plume[J]. Ocean Modelling, 2008, 21(1): 12-21.4 Halverson M J, Pawlowicz R. Estuarine forcing of a river plume by river flow and tides[J]. Journal of Geophysical Research: Oceans (19782012), 2008, 113(C9).5 Tedford E W, Carpenter J R, Pawlowicz R, et al. Observation and analysis of shear instability in the Fraser River estuary[J]. Journal of Geophysical Research: Oceans (19782012), 2009, 114(C11).6 Chao S Y. Wind-driven motion of estuarine plumes[J]. Journal of Physical Oceanography, 1988, 18(8): 1144-1166.7 Fong D A, Geyer W R. The alongshore transport of freshwater in a surface-trapped river plume*[J]. Journal of Physical Oceanography, 2002, 32(3): 957-972.8 Pawlowicz R, Riche O, Halverson M. The circulation and residence time of the Strait of Georgia using a simple mixing box approach[J]. Atmosphere-ocean, 2007, 45(4): 173- 193.9 Kasai A, Kurikawa Y, Ueno M, et al. Salt-wedge intrusion of seawater and its implication for phytoplankton dynamics in the Yura Estuary, Japan[J].
  17. 17. Thanks for your attention!