Towards Operational Coastal Modelling in Australia and New Zealand Presentation Title, Arial Regular 29pt Sub title, Arial Regular 24pt

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1 Towards Operational Coastal Modelling in Australia and New Zealand Presentation Title, Arial Regular 29pt Sub title, Arial Regular 24pt Philip Gillibrand & Mike Herzfeld CSIRO Marine & Atmospheric Research, Hobart Charitha Pattiaratchi University of Western Australia, Crawley Graham Rickard, Stephane Popinet NIWA, Greta Point, Wellington Emily Lane NIWA, Riccarton, Christchurch

2 Acknowledgements CSIRO Environmental Modelling Group: John Parslow, Mike Herzfeld, Karen Wild-Allen, Nugzar Margvelashvili, Farhan Rizwi, John Andrewartha, Emlyn Jones, Jenny Skerratt, Mathieu Mongin NIWA: Rob Bell, Michael Uddstrom

3 Outline Near Real-time (NRT) modelling in Australia Rationale Methods Some example of regional studies Data assimilation The Ribbon model Hindcast modelling in Western Australia Operational Coastal Ocean Modelling in NZ EcoConnect Storm surge forecasting Shared Aspirations and Potential Cooperation

4 Coastal Ocean Observatories Development of coastal observatories Observation networks + operational modelling

5 Near Real-time (NRT) Modelling: Rationale Previous approach: Nominate a hindcast period (usually 1 year) and produce a calibrated model for that period. Problems: Model loses relevance as time goes by. Model is put on the shelf at the project s termination and inaccessible to stakeholders. Difficult to resurrect models as code base evolves. Producing a new hindcast involves considerable effort. NRT approach: Provides a potentially indefinite archive of results long term results may potentially be accumulated. Always remains relevant. May be used to re-run hindcast scenarios for any period it is running (fast models). May run BGC/sediment scenarios for any period within the archive using transport models (slow models). Can use higher resolution since runtime need only be ~2:1. Usually easier to implement since near real-time forcing products are readily available over the web.

6 NRT approach Bathymetry derived from high resolution databases e.g. Geoscience Australia 250 m product Downscale from operational global ocean products Often several nests are required. Supply initial and open boundary conditions (T/S, η, v). Open boundary configuration is critical. Often tidal effects are superimposed. Operational atmospheric models supply surface boundary conditions. Momentum wind stress. Heat flux: Can apply components directly (no feedback). Compute components using bulk schemes, with feedback. Freshwater flux.

7 Ocean and Atmospheric Models Ocean Bluelink project (BoM, CSIRO). OceanMAPS operational product. BRAN data assimilating hindcasts. Global ocean model based on mom4p1 codebase. 10 km resolution in Australasian region. Provides daily means of temperature, salinity, sea level and velocity. Does not include tides, atmospheric pressure or freshwater river input (in Australia). BRAN 3.0 SST and currents in NE Australia Atmosphere ACCESS-A meteorological product, Operationally run by BoM ~12 km resolution. Use surface fields of: Wind stress for momentum boundary condition. Cloud to compute short wave radiation. Pressure, dry & dew point temperature to compute bulk fluxes and longwave radiation. Precipitation for freshwater fluxes. ACCESS 10m winds, reproduced from:

8 Sparse Hydrodynamic Ocean Code (SHOC) General hydrodynamic coastal ocean model Uses a sparse indexing system for memory efficiency Solves 2D or 3D hydrostatic Reynolds-averaged Navier- Stokes equations using finite differences Multiple options available: Rectilinear, curvilinear, polar etc staggered grid Vertical discretization (z-level or sigma-coords) Advection schemes Turbulence closure schemes Open boundary conditions Momentum, heat, freshwater bulk schemes Horizontal mixing (fixed or Smagorinsky) Bottom friction (linear or nonlinear) Integrated into the Environmental Modelling Suite, a coupled hydrodynamic-sediment transportbiogeochemistry modelling system.

9 Multiple nested downscaling A boundary cell ratio of 7:1 is considered the upper bound. Multiple nests may be required to conform to this criterion.

10 Examples: Routine NRT results can be viewed at: e.g. for Storm Bay, D Entrecasteaux, Huon, Derwent South East Queensland GBR Near real-time implementations

11 Leschenault Estuary, W.A. OceanMAPS AVHRR TRIKE

12 Hindcast heuristic calibration example : GBR 36 Moorings 34 Salinity (PSU) Observed and modelled salinity at Yongala National reference station. GBR - surface GBR - 10m depth Observed - 10m depth 24 Dec Jan Feb Mar Apr Tide gauge Satellite Enhanced true colour Burdekin and Herbert Rivers, 19 February 2009.

13 Data streams for calibration and validation Monthly Sampling Glider Transects 42.6 IN F O R M D sam pling Latitude ( S) Near Real Time Moorings & Sensor Networks T A F I sta tio n T A F I sta tio n C M A R g lide r lo n g itu d e ( E )

14 Data assimilation : EnOI Glider track Comparison with GHRSST

15 Ribbon Model

16 Outline Near Real-time (NRT) modelling in Australia Rationale Methods Some example of regional studies Data assimilation The Ribbon model Hindcast modelling in Western Australia Operational Coastal Ocean Modelling in NZ EcoConnect Storm surge forecasting Shared Aspirations and Potential Cooperation

17 Double nesting scheme HYCOM: for oceanic forcing ROMS: for coarse and fine scale modelling HYCOM boundary forcing Coarse model boundary forcing Western Australia Coarse model(wac): Grid resolution: 2~3km Grid size: 538*230 Driven by HYCOM, UCAR wind, NCEP surface heat flux Ningaloo Fine model(nf): Grid resolution: 500m Grid size: 320*200 Driven by Coarse Model, UCAR wind, NCEP surface hear flux

18 ROMS Model performance: Surface temperature and velocity fields the NF model domain on 18-Nov driven by (a) original HYCOM forcing, (b) zero surface elevation and velocity forcing, (c) 10% reduced HYCOM inputs and (d) 30% reduced HYCOM inputs (d).

19 Cross-shore profiles (upwelling event): North-section Middle-section South-section

20 Outline Near Real-time (NRT) modelling in Australia Rationale Methods Some example of regional studies Data assimilation The Ribbon model Hindcast modelling in Western Australia Operational Coastal Ocean Modelling in NZ EcoConnect Storm surge forecasting Adaptive grid modelling in NZ Shared Aspirations and Potential Cooperation

21 EcoConnect Features Decision enabling tool Multi-hazard information system Weather River Flow Sea-state Sea-level Real-time observations Context Other models Forecast accuracy Integrates forecasts and realtime data Alerting Any data type Self administered SMS / No special user requirements: Computational load is at NIWA Flexible

22 EcoConnect Forecast System Global Weather Forecast System Winds Obs. Sea Ice Local Obs. Global Wave Forecast System (GLOBALWAVE) Weather Forecast Wave Forecast System (NZLAM) System (NZWAVE) River-flow Model (TopNet) Ensemble Weather Model Tide Model (NZTIDE) Storm-Surge Model (RiCOM) Inundation Model (RiCOM) Landslide Model Climate Explorer Products Verification System Web Delivery Application Related Models High Performance Computing and Data Management System

23 Hydrodynamic Model Description Key Features: The River and Coastal Ocean Model - RiCOM; Solves the time-dependent Reynolds-averaged Navier Stokes equations in two (depth-averaged) or three (depth-resolving) dimensions; Numerical approach uses mixed finite element and finite volume methods on unstructured grids; Spatial discretization on triangular or pie-shaped finite elements (lowest order Raviert-Thomas). Semi-implicit time-stepping and semi-lagrangian treatment of advection increases model stability; Boundary forcing: MSLP, wind stress, ocean tides; Prognostic variables: SSH, U, V (and W); Current applications: storm surge/sea level tsunami inundation coastal tidal dynamics (aquaculture, tidal energy) Selected References: Walters, R.A., A 3D, finite element model for coastal and estuarine circulation. Cont. Shelf Res. 12, Walters, R.A., Casulli, V., A robust, finite element model for hydrostatic surface water flows. Comm. Num. Meth. Engineer. 14, Walters, R. A., Goring, D. G., Bell, R. G., Ocean tides around New Zealand. NZ J. Mar. Fresh. Res., 35, Walters, R. A., A semi-implicit finite element model for non-hydrostatic (dispersive) surface waves. Int. J. Num. Meth. Fluids 49, Walters, R.A., Lane, E.M., Hanert, E., Time-stepping methods for the Coriolis term in a shallow water model. Ocean Modelling, in press. Walters, R.A., Lane, E.M., Henry, R.F., Semi-Lagrangian methods for a finite element coastal ocean model. Ocean Modelling 19, Lane et al., An Unstructured Grid Ocean Model within the EcoConnect Forecast System. Ocean Modelling, 28,

24 Unstructured Grids Unstructured grids allow variable spatial resolution, permitting a smooth transition from coarsely resolved offshore areas to finely resolved inshore areas, without requiring grid nesting and the creation of artificial boundaries in the interior of the domain u n η u n u v

25 Operational Model Setup Model operates in 2D (depth-averaged) mode; Domain covers most of NZ EEZ; Spatial resolution (element side length) from 40 m 80 km; elements. Surface forcing (MSLP and wind stress) from 12-km operational meteorological model (NZLAM12); Tidal forcing From NZTIDE model in operational system from NAO ocean model in development system; 48-h forecasts made every 12 hours at 0600Z and 1800Z. Event Analysis Concatenate forecasts to analyse events; Cyclone Funa, January 2008; Verification of sea levels and storm surge height; Visualisation of event.

26 Evaluation Against Data Sea Level Storm Surge SSH Storm Surge RMSE d 2 RMSE d 2 Anawhata Charleston Dog Island Green Island Jackson Bay Kaikoura Kaingaroa Kapiti Island L. Kaiteriteri Lyttelton Marsden Point Moturiki Island Model Skill RMS Error: E RMS 1 N = ( p N j= 1 j o j ) 2 N N 2 d 2 = 1 ( p j o j ) ( p j o + o j o ) j= 1 j= Tarakohe Timaru Westgate Port Whitianga Sumner Head Tararu

27 EcoConnect Forecast

28 High-tide exceedance curve: Auckland Tidal prediction 0.6 Data source: Ports of Auckland MLOS = m Tidal residual + seiche = m SS = 0.4 m 23 Jan NZST

29 When it all came together & Auckland got caught Storm-tide event: 23 Jan 2011 NZTA Peter Heyes

30 Outline Near Real-time (NRT) modelling in Australia Rationale Methods Some example of regional studies Data assimilation The Ribbon model Hindcast modelling in Western Australia Operational Coastal Ocean Modelling in NZ EcoConnect Storm surge forecasting Shared Aspirations and Potential Cooperation

31 Contrasts between Approaches Coastal Ocean modelling in Australia NRT and traditional hindcast approaches Multi-disciplinary approach to 3D hydrodynamics, sediment transport and biogeochemistry. Models run in a quasi-operational manner. Regionally based studies, with long-term plan to nest local models in the Ribbon model Structured grids, higher resolution achieved through model nesting. Coastal Ocean Modelling in NZ Operational and traditional hindcast approaches Currently based on predicting weather-related hazards 2D hydrodynamic model only No forecasting of water properties Unstructured grid approach allows for resolution focussing Adaptive grid technology under development

32 Gerris: Adaptive spectral wave modelling

33 Adaptive Grid efficiency

34 Shared Aspirations and Potential for Cooperation Shared Aspiration To develop and implement calibrated (quasi-)operational coastal ocean models for research and resource management purposes. Potential For Cooperation Improved tools and technology Improving model speed & resolution Unstructured/Adaptive grid methods Catchment modelling Coupling hydrodynamics to downstream models Transport models (offline simulations) Flow fields output on unstructured grids Comparative testing and development of new tools