A simple pre-operational model for the portuguese coast

April 16th 2007 G. Riflet, EGU symposium Vienna 2007 1

Assessing the quality of a pre-operational model for the Portuguese coast

Riflet G.1, P.C. Leitão2, A.R. Trancoso3, A. Canas1, R. Fernandes1, L. Fernandes1, A.C. Garcia1, R.J. Neves1

1 – MARETEC, DEMecanica, Instituto Superior Técnico, 1049-001 Lisbon, Portugal ([email protected])

2 – HIDROMOD, Av Manuel da Maia 36 3-e, 1000-201 Lisbon, Portugal ([email protected])

3 – METEO-IST, Secção Energia e Ambiente, DEMecanica, Instituto Superior Técnico, 1049-001 Lisbon, Portugal ([email protected])


• Does the downscaling of large-scale oceanic forecasting solutions allow a reliable way for forcing operational regional and local models? Does it improves the local solutions results? If so, how can we quantify it? These are the fundamental questions that this work tries to tackle partially.

• A pre-operational system was implemented at MARETEC that performs weekly hydrodynamic forecasts of the Portuguese coast and of the Estremadura region. It downscales the Mercator-Océan PSY2V2R1 1/15º solution to a 0.06º and 0.02º domains using the MOHID water modeling system. Tide forced from the FES2004 tidal atlases was added, and atmospheric forcing from a regional scale forecasting system was provided by Meteo-IST for surface forcing. Also, a freshwater discharge was estimated based on a 2006 flow time series from Instituto da Água for simulating the Tagus estuary input.

•The results are analyzed against published evidences, and against tidal station data and SST remote sensing imagery.

Introduction


•Three domains are modeled: a 2D barotropic model of the west Iberia region bounded by [13.7 5.3] ºW x [33.5 46.1] ºN; a 3D baroclinic model of the west Iberia region, nested to the latter, bounded by [12.6 5.5] ºW ; and a 3D baroclinic model of the Estremadura region bounded by [11.2 8.8] ºW x [40.3 37.5] ºN and nested to the latter.•Each domain radiates the water level using a Flather radiation scheme, except for the 2D barotropic model that radiates the level using a Blumberg radiation scheme. •The 3D models initial S and T are directly interpolated from the Mercator-Océan solution. •Atmospheric forcing is imposed with latent and sensible heat fluxes, solar radiation, infrared radiation, atmospheric pressure, evaporation and precipitation coming from the MM5 results from the Meteo-IST model.•The 2D barotropic model has the level forced at the open boundaries by the FES2004 tidal atlas solution. The nested models are forced at the open boundaries with S, T, u, v and η from the father model and/or the Mercator-Océan solution.•A sponge layer is applied near the open boundaries where a Flow Relaxation Scheme is employed and a higher horizontal turbulent viscosity is applied.

Models Setup

On the left panel, the Western Iberia coast baroclinic model bathymetry. Bounded by [12.6 5.5] ºW x [34.4 45.0] ºN. 0.06º spatial resolution, labeled P. On the right panel, Portugal continental central regional coastal model bathymetry. Bounded by [11.2 8.8] ºW x [40.3 37.5] ºN. 0.02º spatial resolution, labeled C. Baseline data from ETOPO 2’.


The application is run weekly and provides 5 day forecast for the three-dimensional hydrodynamic circulation off the coast of Portugal. Results since November 2006 are available at http://data.mohid.com served by an Opendap server and a Live Access Server (LAS). The results shown are either instantaneous values, either a statistical average performed over the available set of weekly runs.Instantaneous results seem to evidence that the finer-scale model is more prone to generate internal waves.

Results

To the left, the interpolated temperature fields of the Mercator solution. To the right, the super-position of the temperature fields of the C model over the P model. The temperature scale's interval is [14.5 20.0] ºC at the surface (top) and [12.0 14.7] ºC at 250 m (bottom). The graphical tool is Mohid GIS.

http://data.mohid.com/

http://data.mohid.com/


The Mediterranean Waters (MW) spreading pathway are evidenced in currents at intermediate depth and with the salinity distribution at 1000 m. The models averaged results seem realistic when compared with observations reported in the literature.

Results

Horizontal distribution of velocity ensemble average at 2 m depth for the top panel and 645 mdepth for the bottom panel. Tw o main branches of the MW spreading pathw ays are w ell pronounced inthe bottom panel. the polew ard slope current branch, and the cyclonic recirculation f low ing southw ard.

Color map and contours of salinity distribution ensemble average at 1000 m depth ranging ininterval [35.6 36.2] showing the spreading pathway of the MO off western Iberia. Contour lines are valued[35.6; 35.78; 35.84; 35.9; 35.96; 36.02; 36.08; 36.14; 36.2]


The Mediterranean outflow (MO) in the model shifts from a bottom current to a buoyancy driven intermediate depth jet current in the Gulf of Cadiz at about 8 ºW. This is a known realistic scenario.

Results

On the left, ensemble averages of meridional velocity contours of 0.1 ms-1 apart and color maps in the interval [-.1 .1] ms-1 are shown. Positive velocities are equatorward and negative velocities are poleward. On the right, ensemble averages of salinity contours of[35.6; 35.66; 35.72; 35.78; 35.84; 35.90; 35.96; 36.02; 36.08; 36.14; 36.2] and color maps in the interval [35.6 36.2] are shown. The plots are zonal sections of the Portuguese coast at 40.95 ºN for the top panels; and 38.25ºN for the bottom panels. The cross sections are shown in the bathymetries figure.

On the left panel, salinity contours of [35.5; 35.52; 35.83; 35.94; 36.05; 36.16; 36.27; 36.38; 36.49; 36.6] and color maps in the interval [35.5 36.6]. On the right panel, ensemble averages of zonal velocity contours of [-.15; -.12; -.09; -.06; -.03; 0; .03; .06; .09;.12; .15] ms -1 and color maps in the interval [-.15 .15] ms -1. The plots are meridional sections in the Gulf of Cadiz at longitude 7.83 ºW. The MO shifts from a bottom current to a buoyancy driven intermediate depth jet current. The cross sections are shown in the bathymetries figure.


Quality assessment can be performed with instantaneous results agains tidal stations and remote-sensing SST imagery.

Results

The Mercator solution sea surface temperature daily average on the September 9th 2006, at the left. A NOAA sea surface temperature satellite image taken during the same day, at the middle. At the right, the Mohid instantaneous solution taken the same day at 19h00 hours. The temperature scale is set to [17ºC 22ºC]. Note that the color palettes diverge between the satellite images and the model's fields. The graphical tool used is Mohid GIS.

00.5

11.5

22.5

33.5

44.5

09-02-200712:00

11-02-200712:00

13-02-200712:00

15-02-200712:00

17-02-200712:00

19-02-200712:00

21-02-200712:00

23-02-200712:00

25-02-200712:00

Time

Water

level (

m)

Sines tide gauge Operational model

Water level from from a tidal station in pink located at 37º57’ ºN and 8º55’ ºW in Sines and illustrated in the the bathymetries figure. Water level from the pre-operational model in forecast mode for the same location. The correlation is 0.99 + 5e-3 and the RMSE is 0.19 + 5e-3 m.


•The MW main spreading pathways seem realistic when compared with observations. Two expected main branches are reproduced by our model. •The salinity spreading pattern at 1000 m depth in our model is typical of other models findings.•The regional model with finer resolution seems to be internal-wave permitting.•The tidal forcing with FES2004 provides an added value to the Mercator-Océan solution.•Comparison with SST imagery seems promising in order to assess the quality of the operational model.

Conclusions• Perform calculus continuation instead of weekly spin-up;• Calculate mass fluxes in predefined cross-sections;• Calculate TKE;• Acquire SST from remote-sensing data (MODIS, MERIS);• Gather available CTD, ADCP and RAFOS data in order to compare with the models results;• Perform further analysis of the models results against in-situ tidal stations data,• Implement the data plotting of the results operationally;• Eventually, implement a digital filter for the calculation of stable non-trivial initial conditions.

Future work


The authors w ish to thank Mercator-Océan for providing the ocean forecasts and reanalysis (http.//w w w .mercator-ocean.fr/),Meteo-IST (in particular J. J. Delgado Domingos) for providing the atmospheric forecasts (http.//meteo.ist.utl.pt/),Hidromod, for providing logistical support and in-situ data (http.//w w w .hidromod.pt/).This w ork is funded by the EU in the framew ork of FP6 GMES activities according the terms of the contract SST4-CT-2005-012336 (INSEA project). This w ork is funded by the EU in the framew ork of INTERREG III-B Espaço-Atlântico activities (EROCIPS and 207-EASY projects).G. Rif let, A.R. Trancoso and A. Canas acknow ledge grants SFRH/BD/17631/2004, SFRH/BD/17957/2004 and SFRH/BD/14185/2003, respectively, f rom Fundação para a Ciência e Tecnologia.

Acknowledgements

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A simple pre-operational model for the portuguese coast

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