The Regional Ocean Modelling System (ROMS) has been tested in The Regional Ocean Modelling System (ROMS) has been tested in

Bilbao harbour located in the east corner of the Bay of Biscay, Bilbao harbour located in the east corner of the Bay of Biscay,

northern Spain. In this study, the inner harbour hydrodynamics, northern Spain. In this study, the inner harbour hydrodynamics,

as observed through oceanographic measurements, has been as observed through oceanographic measurements, has been

numerically replicated. Measurements show seasonal differences numerically replicated. Measurements show seasonal differences

which which have been used to define the climatology input to the have been used to define the climatology input to the

modelling process. Moreover, daily NCEP reanalysis data have modelling process. Moreover, daily NCEP reanalysis data have

been used as atmospheric forcing. The numerical results are in been used as atmospheric forcing. The numerical results are in

good agreement with the hydrodynamic measurements showing good agreement with the hydrodynamic measurements showing

the suitability of ROMS in the study of coastal hydrodynamics with the suitability of ROMS in the study of coastal hydrodynamics with

a high resolution.a high resolution.

Key Words:Key Words: Coastal Modelling, Harbour Hydrodynamics, ROMS, Seasonal Coastal Modelling, Harbour Hydrodynamics, ROMS, Seasonal

Differences.Differences.

1. INTRODUCTION1. INTRODUCTION

5. CONCLUSIONS AND FUTURE WORK5. CONCLUSIONS AND FUTURE WORK

2. HYDRODYNAMIC BEHAVIOUR2. HYDRODYNAMIC BEHAVIOUR

4. RESULTS4. RESULTS

3. MODELLING CHARACTERISTICS3. MODELLING CHARACTERISTICS

BIBLIOGRAPHYBIBLIOGRAPHY

HARBOUR HYDRODYNAMIC MODELLING WITH ROMS:HARBOUR HYDRODYNAMIC MODELLING WITH ROMS:BILBAO CASE STUDYBILBAO CASE STUDY

Luis FerrerLuis Ferrer11, Manel Grifoll, Manel Grifoll11, Manuel González, Manuel González11, Manuel Espino, Manuel Espino22

11Unidad de Investigación Marina, AZTI-Tecnalia, Herrera Kaia – Portu aldea z/g, 20110, Pasaia – Gipuzkoa, Spain Unidad de Investigación Marina, AZTI-Tecnalia, Herrera Kaia – Portu aldea z/g, 20110, Pasaia – Gipuzkoa, Spain 22Laboratori d’Enginyeria Marítima (LIM), Universitat Politènica de Catalunya, Jordi Girona s/n, 08023, Barcelona, Spain Laboratori d’Enginyeria Marítima (LIM), Universitat Politènica de Catalunya, Jordi Girona s/n, 08023, Barcelona, Spain

The model configuration has a mean horizontal The model configuration has a mean horizontal

resolution of approx. resolution of approx. 32 32 m and 5 vertical sigma m and 5 vertical sigma

levels in depth (Figure 6). Initial and boundary levels in depth (Figure 6). Initial and boundary

temperature and salinity conditions were derived temperature and salinity conditions were derived

from seasonal hydrographical observations from seasonal hydrographical observations

measured inside the harbour. The atmospheric measured inside the harbour. The atmospheric

forcing was provided by daily NCEP reanalysis forcing was provided by daily NCEP reanalysis

data: 10m winds, surface air pressure, 2m data: 10m winds, surface air pressure, 2m

temperature and relative humidity, and net temperature and relative humidity, and net

shortwave and downward longwave radiations. shortwave and downward longwave radiations.

Air-sea heat and momentum fluxes were Air-sea heat and momentum fluxes were

calculated by the bulk formulae of Fairall calculated by the bulk formulae of Fairall et al.et al.

(2003). The inflow of the Nervion river was (2003). The inflow of the Nervion river was

specified as monthly climatologic values.specified as monthly climatologic values. Tidal Tidal

forcing was included in the simulation according forcing was included in the simulation according

to the data from the OSU Topex/Poseidon Global to the data from the OSU Topex/Poseidon Global

Inverse Solution version 5.0 (TPXO.5).Inverse Solution version 5.0 (TPXO.5).

The reclamation of large harbour platforms for The reclamation of large harbour platforms for

industrial, economic and commercial industrial, economic and commercial

activities, in addition to nautical and activities, in addition to nautical and

recreational purposes, implies changes in recreational purposes, implies changes in

their hydrodynamic behaviour and strongly their hydrodynamic behaviour and strongly

influences their water quality. This is the case influences their water quality. This is the case

of the Bilbao harbour, locatedof the Bilbao harbour, located in the inner part in the inner part

of the Nervion river estuary (Figure 1), which of the Nervion river estuary (Figure 1), which

has been growing progressively to the outer has been growing progressively to the outer

estuarine and open sea areas, becoming one estuarine and open sea areas, becoming one

of the largest harbours of the continent of the largest harbours of the continent

(Figure 2). (Figure 2). The history of the harbour might The history of the harbour might

well be told as a continuous voyage sailing out well be told as a continuous voyage sailing out

to the sea.to the sea.

Figure 1. Aerial photography of Nervion estuary

Figure 2. Bilbao harbour: past and present.

Figure 6. Harbour bathymetry.

The eight primary harmonic constituents (M2, S2, N2, K2, K1, O1, P1, Q1) were The eight primary harmonic constituents (M2, S2, N2, K2, K1, O1, P1, Q1) were

introduced in ROMS through the open boundaries using the Flather condition introduced in ROMS through the open boundaries using the Flather condition

(Marchesiello (Marchesiello et alet al., 2001). In forecast mode, the model output data were automatically ., 2001). In forecast mode, the model output data were automatically

acquired from the hourly history fields and daily averaged fields.acquired from the hourly history fields and daily averaged fields.

ABSTRACTABSTRACT

ACKNOWLEDGEMENTSACKNOWLEDGEMENTS

Figure 5. Density and temperature profiles during winter and summer (2004-2005).

Figure 4. Sea-level measurements recorded at Bilbao harbour

Figure 3. Surface currents (with and without tides) inside the Bilbao harbour

This work has been carried out with partial financial support from different sources of the Basque This work has been carried out with partial financial support from different sources of the Basque

Government (Departamento de Agricultura, Pesca y Alimentación; Departamento de Medio Government (Departamento de Agricultura, Pesca y Alimentación; Departamento de Medio

Ambiente y Ordenación del Territorio; Departamento de Industria, Comercio y Turismo and Ambiente y Ordenación del Territorio; Departamento de Industria, Comercio y Turismo and

Departamento de Educación, Universidades e Investigación), and the Ministerio de Ciencia y Departamento de Educación, Universidades e Investigación), and the Ministerio de Ciencia y

Tecnología (Spain).Tecnología (Spain). The authors acknowledge the NCEP reanalysis data provided by the The authors acknowledge the NCEP reanalysis data provided by the

NOAA/OAR/ESRL PSD (NOAA/OAR/ESRL PSD (www.cdc.noaa.gov). In addition, thanks to the ESEOO project (). In addition, thanks to the ESEOO project (www.eseoo.org) )

for providing a research reference in Operational Oceanography and the Bilbao Harbour Authority for providing a research reference in Operational Oceanography and the Bilbao Harbour Authority

for the logistical support (for the logistical support (www.bilbaoport.es). ).

This work shows the suitability of the ROMS numerical code This work shows the suitability of the ROMS numerical code

for small scale areas. Using specific monthly climatology for small scale areas. Using specific monthly climatology

information for the harbour and forcing input provided by information for the harbour and forcing input provided by

the daily NCEP reanalysis data, the model reproduces the daily NCEP reanalysis data, the model reproduces

reasonably well the hydrodynamic behaviour inside the reasonably well the hydrodynamic behaviour inside the

harbour and the seasonal differences observed in the harbour and the seasonal differences observed in the

vertical density profiles. These results are considered as a vertical density profiles. These results are considered as a

starting point for the implementation of an operational starting point for the implementation of an operational

system in the harbour; i.e. a tool for the environmental system in the harbour; i.e. a tool for the environmental

management of the water quality (Figure 9). As to the management of the water quality (Figure 9). As to the

hydrodynamic modelling, further work in model calibration, hydrodynamic modelling, further work in model calibration,

verification and data assimilation would be necessary to verification and data assimilation would be necessary to

achieve this goal. achieve this goal.

The hydrodynamic behaviour of Bilbao harbour The hydrodynamic behaviour of Bilbao harbour

is characterised by the tidal dynamics, the is characterised by the tidal dynamics, the

baroclinic component observed in the CTD baroclinic component observed in the CTD

vertical profiles, and the wind stresses that vertical profiles, and the wind stresses that

play an important role in the currents in the play an important role in the currents in the

outer zone of the harbour (Figure 3). Tides are outer zone of the harbour (Figure 3). Tides are

defined as low and high mesotidal during neap defined as low and high mesotidal during neap

and spring tides respectively (Figure 4). The and spring tides respectively (Figure 4). The

vertical density structure presents two main vertical density structure presents two main

characteristic situations (Figure 5): a) during characteristic situations (Figure 5): a) during

winter, a homogeneous density structure winter, a homogeneous density structure

dominates; b) whilst during summer, a dominates; b) whilst during summer, a

considerable vertical density gradient is considerable vertical density gradient is

observed.observed.

The hydrodynamics of Bilbao harbour has been simulated The hydrodynamics of Bilbao harbour has been simulated

with ROMS (with ROMS (Shchepetkin and McWilliams, 2005Shchepetkin and McWilliams, 2005) for two ) for two

weeks during the winter and summer of 2005. Results weeks during the winter and summer of 2005. Results

obtained for the 3rd January and the 4th July are shown obtained for the 3rd January and the 4th July are shown

on Figures 7 and 8. on Figures 7 and 8.

Comparison between the numerical results and the Comparison between the numerical results and the

hydrodynamic data from surveys, shows that the model hydrodynamic data from surveys, shows that the model

reproduces well, (i) the temperature values measured reproduces well, (i) the temperature values measured

during the winter and summer in the harbour domain during the winter and summer in the harbour domain

(Figure 7.2 and 8.2); (ii) the presence of the stratified (Figure 7.2 and 8.2); (ii) the presence of the stratified

vertical structure during summer (Figure 8.6) and; (iii) a vertical structure during summer (Figure 8.6) and; (iii) a

well-mixed structure during the winter (Figure 7.6). well-mixed structure during the winter (Figure 7.6).

The vertical structure of the water column during summer The vertical structure of the water column during summer

is associated to the increase of the heat transfer at the is associated to the increase of the heat transfer at the

sea surface and the consequent rising of the water sea surface and the consequent rising of the water

temperature. This process in sheltered zones tends to temperature. This process in sheltered zones tends to

produce the presence of a thermocline in the vertical produce the presence of a thermocline in the vertical

profile (Bowden, 1983). The salinity field structure at sea profile (Bowden, 1983). The salinity field structure at sea

surface decreases in the inner harbour zone due to the surface decreases in the inner harbour zone due to the

freshwater discharge of the Nervion river, especially in freshwater discharge of the Nervion river, especially in

the winter season. the winter season.

The current fields are obtained by averaging daily the The current fields are obtained by averaging daily the

hourly history velocity fields (Figures 7.1 and 7.3 during hourly history velocity fields (Figures 7.1 and 7.3 during

winter and Figures 8.1 and 8.3 during summer). The winter and Figures 8.1 and 8.3 during summer). The

averaged current fields are characterised by a complex averaged current fields are characterised by a complex

flow in winter due to the strong winds in the interest area flow in winter due to the strong winds in the interest area

and the frequent freshwater discharge from the river, in and the frequent freshwater discharge from the river, in

addition to the irregular topography of the harbour. In addition to the irregular topography of the harbour. In

summer conditions, the current fields are smoother than summer conditions, the current fields are smoother than

in winter, due to the weaker winds and the decrease in in winter, due to the weaker winds and the decrease in

the river runoff.the river runoff.

Figure 7. Numerical results during 3rd January 2005. Figure 8. Numerical results during 4th July 2005.

Figure 7.1. Eastward averaged velocity (m/s). Figure 7.2. Sea surface temperature (ºC).

Figure 7.4. Sea surface salinity (PSU).Figure 7.3. Northward averaged velocity (m/s).

Figure 7.5. Northward averaged velocity A-B. Figure 7.6. Temperature A-B.

Figure 8.1. Eastward averaged velocity (m/s). Figure 8.2. Sea surface temperature (ºC).

Figure 8.4. Sea surface salinity (PSU).Figure 8.3. Northward averaged velocity (m/s).

Figure 8.5. Northward averaged velocity A-B. Figure 8.6. Temperature A-B.

Figure 9. Harbour water quality management system.

Bowden, K.F., 1983. Bowden, K.F., 1983. Physical Oceanography of Coastal WatersPhysical Oceanography of Coastal Waters. John Wiley & Sons. Baffins Lane. . John Wiley & Sons. Baffins Lane.

West Sussex. England. 301 p. Fairall, C.W., Bradley, E.F., Hare, J.E., Grachev, A.A., Edson, J.B., 2003. West Sussex. England. 301 p. Fairall, C.W., Bradley, E.F., Hare, J.E., Grachev, A.A., Edson, J.B., 2003.

Bulk parameterization of air-sea fluxes: updates and verification for the COARE algorithm.Bulk parameterization of air-sea fluxes: updates and verification for the COARE algorithm. J. J.

Climate, 16 (4), 571-591.Climate, 16 (4), 571-591.

Marchesiello, P., McWilliams, J.C., Shchepetkin, A., 2003. Marchesiello, P., McWilliams, J.C., Shchepetkin, A., 2003. Equilibrium structure and dynamics of the Equilibrium structure and dynamics of the

California current system.California current system. J. Phys. Oceanogr., 33, 753-783. J. Phys. Oceanogr., 33, 753-783.

Shchepetkin, A.F., McWilliams, J.C., 2005. Shchepetkin, A.F., McWilliams, J.C., 2005. The regional oceanic modeling system (ROMS): a split-The regional oceanic modeling system (ROMS): a split-

explicit, free-surface, topography-following-coordinate oceanic modelexplicit, free-surface, topography-following-coordinate oceanic model. Ocean Model., 9, 347-404.. Ocean Model., 9, 347-404.

Hydrodynamic Hydrodynamic modellingmodelling

Risk analysisRisk analysis

Transport Transport evaluationevaluation

USERSUSERS

Water Quality Water Quality Environment Environment

SystemSystem(operational mode)(operational mode)

Real time forecastsReal time forecasts

Real time field dataReal time field data

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