Scientia Marina, Vol 76, No 3 (2012)

Monitoring the Northern Current in the Gulf of Lions with an observing system simulation experiment

Aurélie Duchez
LEGI - National Oceanography Centre, University of Southampton , France

Jacques Verron
LEGI , France

Jean-Michel Brankart
LEGI , France

Yann Ourmières
LSEET , France

Philippe Fraunié
LSEET , France


The coastal circulation in the Gulf of Lions (GoL) is influenced by the Northern Current (NC), forced by a complex wind system and also affected by important river discharges from the Rhône River. Correct modelling of this current is therefore important for obtaining a good representation of the gulf circulation. An observing system simulation experiment using the SEEK filter data assimilation method was used in a regional 1/16° configuration of the GoL in the NEMO model. The synthetic observation database used for the experiment comprised altimetric data in addition to in-situ temperature and salinity profiles. Statistical diagnostics and other physical criteria based on the improvement of NC representation were set up in order to assess the quality of this experiment. Comparisons between the free 1/16° simulation and the experience with assimilation show that data assimilation significantly improved the description of the characteristics of the NC as well as its seasonal and mesoscale variability, which in turn improved the description of the water exchanges between the coastal region and the open sea.


data assimilation; SEEK filter; OSSEs; Gulf of Lions; Northern Current; coastal processes; high-resolution modelling

Full Text:



Albérola C., Millot C., Font J. 1995. On the seasonal and mesoscale variabilities of the northern current during the PRIMO-0 experiment in the western Mediterranean Sea. Oceanol. Acta 18(2): 163-192.

André G., Garreau P., Garnier V., Fraunié P. 2005. Modelled variability of the sea surface circulation in the western Mediterranean sea and In the gulf of Lions. Ocean Dyn. 55: 458-475.

Auclair F., Marsaleix P., Estournel C. 2001. The penetration of the Northern Current over the Gulf of Lions (Mediterranean) as a downscaling problem. Oceanol. Acta 24: 529-544.

Béranger K., Mortier L., Crépon M. 2005. Seasonal variability of water transport through the Straits of Gibraltar, Sicily and Corsica, derived from a high-resolution model of the Mediterranean circulation. Prog. Oceanogr. 66: 341-364.

Béranger K., Drillet Y., Houssais M.-N., Testor P., Bourdallé-Badie R., Alhammoud B., Bozec A., Mortier L., Bouruet-Aubertot P., Crépon M. 2010. Impact of the spatial distribution of the atmospheric forcing on water mass formation in the Mediterranean Sea. J. Geophys. Res. 115: C12041. PMid:20463844    PMCid:2867361

Berné S., Satra C. 2002. Carte morpho-bathymétrique du Golfe du Lion. Notice explicative. Edition IFREMER Région Languedoc-Roussillon, 48 pp.

Béthoux J., Durrieu de Madron X., Nyffeler F., Tailliez D. 2002. Deep water in the Western Mediterranean: peculiar 1999 and 2000 characteristics, shelf formation hypothesis, variability since 1970 and geochemical inferences. J. Mar. Syst. 33-34: 117-131.

Birol F., Cancet M., Estournel C. 2010. Aspects of the seasonal variability of the Northern Current (NW Mediterranean Sea) observed by altimetry. J. Mar. Syst. 81: 297-311.

Blanke B., Delecluse P. 1993. Variability of the tropical atlantic ocean simulated by a general circulation model with two different mixed-later physics. J. Phys. Oceanogr. 23: 1363-1388.<1363:VOTTAO>2.0.CO;2

Bouffard J., Vignudelli S., Herrmann M., Lyard F., Marsaleix P., Menard Y., Cipollini P. 2008. Comparison of ocean dynamics with a regional circulation model and improved altimetry in the North-Western Mediterranean. Terr. Atmos. Ocean. Sci. 19: 117-133.

Brankart J.M., Testut C.E., Brasseur P., Verron J. 2003. Implementation of a multivariate data assimilation scheme for isopycnic coordinate ocean models: Application to a 1993-96 hindcast of the North Atlantic Ocean circulation. J. Geophys. Res. 108: 3074.

Brasseur P. 2006. Ocean Data Assimilation using Sequential Methods based on the Kalman Filter. In: Verron J., Chassignet E. (eds.), GODAE, an Integrated View of Oceanography: Ocean Weather Forecasting in the 21st Century. Kluwer Academic Press, pp. 577.

Brasseur P., Bahurel P., Bertino L., Birol F., Brankart J.M., Ferry N., Losa S., Remy E., Schröter J., Skachko S., Testut C.E., Tranchant B., Van Leeuwen P.J., Verron J. 2005. Data assimilation for marine monitoring and prediction: the Mercator operational assimilation systems and the MERSEA developments. Q. J. R. Meteorol. Soc. 131: 3561-3582.

Brasseur P., Verron J. 2006. The SEEK filter method for data assim ilation in oceanography: a synthesis. Ocean Dyn. 38(2): 93-121.

Brusdal K., Brankart J.M., Halberstadt G., Evensen G., Brasseur P., Van Leeuwen P.J., Dombrowsky E., Verron J. 2003. A demonstration of ensemble-based assimilation methods with a layered OGCM from the perspective of operational ocean forecasting systems. J. Mar. Syst. 40-41: 253-289.

Conan P., Millot C. 1995. Variability of the northern current off Marseilles, Western Mediterranean Sea from February to June 1992. Oceanol. Acta 18(2): 193-205.

Cummings J., Bertino L., Brasseur P., Dombrowsky E., Fukumori I., Martin M., Kamachi M., Mogensen K., Oke P., Verron J., Weaver A. Ocean data assimilation systems for GODAE. Oceanography. 22. No3.

Drillet Y., Bourdallé-Badie R., Siefridt L., Le Provost C. 2005. Meddies in the Mercator North Atlantic and Mediterranean Sea eddy-resolving model. J. Geophys. Res. 110: C03016.

Duchez A. 2011. Contrôle de la circulation du golfe du Lion par l’altimétrie d’AltiKa : une approche par simulation du système d’observation. Ph.D. thesis, Univ. Toulon Var, 265 pp.

Dufau-Julliand C., Marsaleix P., Petrenko A., Dekeyser I. 2004. Three-dimensional modeling of the Gulf of Lions’ hydrodynamics (northwest Mediterranean) during January 1999 (MOOGLI3 experiment) and late winter 1999: Western Mediterranean Intermediate Water’s (WIW’s) formation and its cascading over the shelf break. J. Geophys. Res. 109, C11, 002.

Echevin V., Crépon M., Mortier L. 2003. Simulation and analysis of the mesoscale circulation in the northwestern Mediterraean Sea. Ann. Geophys. 21: 281-297.

Estournel C., Broche P., Marsaleix P., Devenon J.L., Auclair F., Vehil R. 2001. The Rhône River plume in unsteady conditions: numerical and experimental results. Estuar. Coast. Shelf Sci. 53: 25-38.

Estournel C., Durrieu de Madron X., Marsaleix P., Auclair F., Julliand C., Vehil R. 2003. Observation and modelisation of the winter coastal oceanic circulation in the Gulf of Lions under wind conditions influenced by the continental orography (FETCH experiment). J. Geophys. Res. 108(C3), 8059.

Flexas M., Durrieu de Madron X., Garcia M., Canals M., Arnau P. 2002. Flow variability in the Gulf of Lions during the matter HFF experiment (March-May 1997). J. Mar. Syst. 33-34: 197-214.

Hu Z. Y., Doglioli A., Marsaleix P., Dekeyser I. 2009. Numerical simulation of eddies in the Gulf of Lions. Ocean Modelling 28: 203-208.

Jacob D., Andrae U., Elgered G., Fortelius C., Graham L.P., Jackson S.D., Karstens U., Koephen C., Lindau R., Podzun R., Rockel B., Rubel F., Sass H.B., Smith R.N.D., Van den Hurk B.J.J.M., Yang X. 2001. A comprehensive model intercomparison study investigating the water budget during the BALTEXPIDCAP period. Meteorol. Atmosp. Phys. 77 (1-4): 19-43.

Johns B., Marsaleix P., Estournel C., Vhil R. 1992. On the wind–driven coastal upwelling in the Gulf of Lions. J. Mar. Syst. 3: 309-329.

Jordi A., Orfila A., Basterretxa G., Tintoré J. 2005. Shelf-slope exchanges by frontal variability in a steep submarine canyon. Prog. Oceanogr. 66(2-4): 120-141.

Langlais C. 2007. Etude de la variabilité interannuelle des échanges côte-large: simulation haute resolution de la dynamique du Golfe du Lion. Ph.D. thesis, Univ. Toulon Var, 282 pp.

Langlais C., Barnier B., Molines J.M., Fraunié P., Jacob D., Kotlarski S. 2009. Evaluation of a dynamically downscaled atmospheric reanalyse in the prospect of forcing long term simulations of the ocean circulation in the Gulf of Lions. Ocean Modelling 30: 270-286.

Large W.G., Yeager S.G. 2004. Diurnal to decadal global forcing for ocean and sea-ice models. NCAR technical notes, 18-221.

Lellouche J. M., Greiner E., Benkiran M. October 2005. PSY2V2, Le nouveau prototype opérationnel haute résolution de Mercator. Mercator-Océan Newsletter, No19.

Madec G. 2008. NEMO Ocean General Circulation Model reference Manuel. Internal Report. LODYC/IPSL, Paris.

MEDAR/MEDATALS 2002 Database. Cruise inventory, observed and analysed data of temperature and bio-chemical parameters (4 CD-ROMS).

Millot C. 1979. Wind induced upwellings in the Gulf of Lions. Oceanol. Acta 2(3): 261-274.

Millot C., Crépon M. 1981. Inertial oscillations on the continental shelf of the Gulf of Lions – observation and theory. J. Phys. Oceanogr. 11(5): 639-657.<0639:IOOTCS>2.0.CO;2

Millot C. 1990. The Gulf of Lions’ hydrodynamics. Cont. Shelf Res. 10(9-11): 885-894.

Mounier F., Echevin V., Mortier L., Crépon M. 2005. Analysis of the mesoscale circulation in the occidental Mediterranean Sea during winter 1999-2000 given by a regional circulation model. Prog. Oceanogr. 66(2-4): 251-269.

Ourmières Y., Brankart J.M., Berline L., Brasseur P., Verron J. 2006. Incremental Analysis Update implementation into a sequential ocean data assimilation system. J. Atmos. Ocean Tech. 23(12): 1729-1744.

Ourmières Y., Zakardjian B., Béranger K., Langlais C. 2011. Assessment of a NEMO-based downscaling experiment for the North-Western Mediterranean region: Impacts on the Northern Current and comparison with ADCP data and altimetry products. Ocean Modelling 39: 386-404.

Petrenko A. 2003. Variability of circulation features in the Gulf of Lion NW Mediterranean Sea. Importance of inertial currents. Oceanol. Acta 26: 323-338.

Petrenko A., Leredde Y., Marsaleix P. 2005. Circulation in a stratified and wind-forced Gulf of Lions, NW Mediterranean Sea: in situ and modelling data. Cont. Shelf Res. 25: 7-27.

Pinardi N., Allen I., De Mey P., Korres G., Lascaratos A., Le Traon P.Y., Maillard C., Manzella G., Tziavos C. 2003. The Mediterranean Ocean Forecasting System: first phase of implementation (1998-2001). Ann. Geophys. 21: 1, 3-20.

Pham D.T., Verron J., Roubaud M.C. 1998. A Singular Evolutive Kalman filter for data assimilation in oceanography. J. Mar. Syst. 16: 323-340.

Reffray G., Fraunié P., Marsaleix P. 2004. Secondary flow induced by wind forcing in the Rhône region of freshwater influence. Ocean Dyn. 54: 179-196.

Uppala S. M., Kallberg P., Simmons A., Andrae U., Bechtold V. D. C., Fiorino M., Gibson J., Haseler J., Hernandez A., Kelly G., Li X., Onogi K., Saarinen S., Sokka N., Allan R., Andersson E., Arpe K., Balmaseda M., Beljaars A., Berg L.V.D., Bidlot J., Bormann N., Caires S., Chevallier F., Dethof A., Dragosavac M., Fisher M., Fuentes M., Hagemann S., Holm E., Hoskins B., Isaksen L., Janssen P., Jenne R., McNally A., Mahfouf J.-F., Morcrette J.-J., Rayer N., SaundersR., Simon P., Sterl A., Trenberth K., Untch A., Vasiljevic D., Viterbo P., Woollen J. 2005. The era-40 re-analysis, Q. J. R. Meteorol. Soc. 131 : 2961-3012.

Vincent P., Steunou N., Caubet E., Phalippou L., Rey L., Thouvenot E., Verron J. 2006. AltiKa: a Ka-band altimetry payload and system for operational altimetry during the GMES period. Sensors. 6: 208-234.

Copyright (c) 2012 Consejo Superior de Investigaciones Científicas (CSIC)

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Contact us

Technical support