Assimilation op©rationnelle et analyse de donn©es glider 2) gliders et etudes de processus...

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  • assimilation oprationnelle et analyse de donnes glider 2) gliders et etudes de processus 1) donnees in-situ gliders ???
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  • Assimilation de donnes glider 1) Premiers essais et assimilation des donnees gliders routiniere dans le cadre de projet d'oceanographie operationnelle: Projets europeens MFSTEP (2004-2005) et MERSEA (2006-2008) IFM-GEOMAR, LPO et IMEDEA 2) Experience specifique d'assimilation de donnees glider dans le cadre de MFSTEP INGV, IFM-GEOMAR, SIO Dobricic et al. (2010) 3) Specificites des donnes gliders (action LEFE-Assim) LOCEAN - simulateur de glider dans un OGCM, L'Heveder et al (2009 & in prep) - assimilation lagrangienne Taillandier et al (2009)
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  • Coriolis ftp server Data Access http://www.ifm.uni-kiel.de/fb/fb1/po2/research/mersea/gliders/spray004_position.html http://www.coriolis.eu.org/cdc/dataSelection/cdcDataSelections.asp Mersea In-Situ Portal data visualization Coriolis data selection website data visualization and download
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  • Quality Control and Metadata QC procedures at Coriolis like for profiling floats. Profiles are considered as vertical. - T and S outsiders based on historical data - Density inversions are rejected + visual inspection Metadata: Vehicle name, project, PI Waypoint (heading) Angle of ascent/descent Target depth Climb depth Target altitude Time between surfacing Current correction Dive #260 dirt in the conductivity cell (1/400)
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  • Assimilation of glider data Temperature differences between MERCATOR North Atlantic 1/15 and the in-situ observations Before data assimilation After data assimilation glider The model trajectory is modified by the data assimilation process, to better fit the observations. development required to better assimilate in-situ data at the moment: correlation criteria for profiling floats 1 profile per 1x1 per week >> in progress
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  • Assimilation de donnes glider en mer Ionienne (MFSTEP) Assimilation des donnees TS et courants moyens (derive residuelle)
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  • Assimilation de donnes glider en mer Ionienne (MFSTEP) Daily averaged vertical profiles along the path of the glider for the period October-December 2004. - Upper panel: glider observations, averaged daily; - Middle panel: control daily analyses. - Lower panel: glider assimilation analyses. temperatur e salinity
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  • Assimilation de donnes glider en mer Ionienne (MFSTEP) Temperature de surface avec et sans assimilation de donnees glider Meilleure representation de l'ecoulement a meso-echelle
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  • Assimilation de donnes glider en mer Ionienne (MFSTEP) Impact a grande echelle des donnees glider Daily averaged sea level differences between glider and control experiments (cm). The differences are shown at the end of each of six months following the introduction of glider observations.
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  • Assimilation de donnes glider en mer Ionienne (MFSTEP) Simulateur de gliders dans MERCATOR Modele de vol quasi-statique
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  • Assimilation de donnes glider en mer Ionienne (MFSTEP) Specificites des donnees glider pour l'assimilation haute resolution et caractere lagrangien Tous les 2 jours donnes (TS, dr) gliders. ces perturbations sont propages dans le champ de courant gostrophique associ. Aprs trois mois danalyse: champ de masse 4D, Des structures de moyenne chelle apparaissent le long de la cte continentale, bordant un dme deau dense qui couvre la partie centrale du bassin. Ces structures documentent les fluctuations du jet gostrophique port en bordure de ce rservoir deau dense. Structures de grande chelle et de moyenne chelle caractristiques de la circulation hivernale sur cette faade nord Mditerranenne mieux representes grace au rseau de surveillance gliders mis en place lors de la campagne EGO2008. analyse squentielle dtats gostrophiques successifs partir des gradients de densit, et indirectement dduits partir de la drive rsiduelle dans la direction normale du transect. L 20km t o 2d t o + 2d t o + 4d toto V Glider 25km/d moyenne et la variance 150m de la salinit. RECONSTRUCTION A PARTIR DES DONNEES IN-SITU EGO2008 To be continued...
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  • Analyse de donnees glider Exemple de l'experience glider Vocals-Peru: Caracterisation de circulations de submesoechelle dans le systeme d'upwelling du Perou Pietri et al. (in prep)
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  • Peruvian Upwelling VOCALS: Ocean-Cloud-Atmoshpere-Land-Study on the Southeast Pacific Climate System VOCALS-Rex-Peru: International multidisciplinary field experiment (CTD and ADCP - 15 days ) Meso-scale sampling 2 months glider's deployment for the fisrt time in this region.
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  • Vertical Sections 9 sections 100km 200m ~ 5 days DENSITY SALINITY OXYGEN FLUORESCENCE TURBIDITY TEMPERATURE (a) (b)
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  • Salinity Stripes Ekman transport, advect surface water offshore: ~ 0.2 Sv
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  • Salinity Stripes v ek ~ 0.1 m/s Ekman transport, advect surface water offshore: ~ 0.1 m/s ~ 0.2 Sv ek ~ 20m
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  • To compensate, a subsurface coastward current appears: V return = V ek ~ 0.01m/s ~ 1km/day Salinity Stripes v ek ~ 0.1 m/s Ekman transport, advect surface water offshore: ~ 0.1 m/s ~ 0.2 Sv return ~ 200m v return ~ 0.01 m/s ek ~ 20m ek return
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  • Salinity Stripes
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  • ~ 5km in 4 days
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  • Salinity Stripes Propagation towards the shore ~ 1.5 cm/s
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  • evidence of vertical motion: Quasi vertical stripes of high and low salinity. High fluorescence and turbidity up to 70m deep. Vertical motion Mixing phenomenum creating cross isopycnal stripes Scale of the phenomenum: 25- 30km
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  • Other mechanism (Thomas and Lee, 2005): Advection of surface dense coastal water Destabilization of the water column -> wind driven buoyancy flux Mixing by convection -> ageostrophic secondary circulations Thomas and Lee (2005) Vertical motion
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  • Density filter: Weighted moving average (15km*2m) Elimination of ageostrophic process Absolute geostrophic velocities
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  • Estimates of absolute gostrophic currents: Smoothed density gradient Thermal wind relation: Glider mean current (integrated on the water column) used as a reference Absolute geostrophic velocities Perpendicular projection of the "glider" mean current. Filter: moving average on a 45h period
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  • Glider section 2 (form October 08 th to 12 th ) (cm/s) Absolute geostrophic velocities (m/s) Humboldt Current: Nothward (Equator) Maximum speed: 30 cm/s Peru Chili Undercurrent: Situated above the continental slope Southward (Pole) Maximum speed on the section: 15 cm/s ADCP onboard R/V Jose Olaya on the same section (October 12 th )
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  • Ageostrophic secondary circulation Two-dimensional Potential Vorticity: Negative PV at the front: Strong vertical shear Horizontal density gradient Cross-front width : ~ 30 km -> coherent with the scale of the salinity stripes vertical circulation: subduction on the dense side of the front upwelling along the frontal interface
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  • Meridional feature du 14 au 16 Novembre 200km long filament meridional phenomenum crossed by the glider
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  • Observational evidence of circulation features - Observation of the upwelling front at very high resolution (200m horiz, 5 days, 100km sections) with physical and biogeochemical parameters. - Estimates of absolutes geostrophic currents Surface current: umax ~20 cm/s, L~40km, z~100m Under current: umax~15 cm/s,L>50km, z>150m - Evidence of a return flow - Evidence of vertical motion at submesoscale wind driven ageostrophic secondary circulations.
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  • Conclusions Oceanographie operationelle & gliders Chaine deja operationnelle & benefice certain (repetitivite des mesures) Couverture deja globale (Testor et al., OceanObs09) sous-exploite pour les modeles 'globaux' Ideal pour les modeles regionaux/cotiers a haute resolution Etudes de processus outil de mesure a haute resolution spatiale et temporelle. Vision verticale de la colonne d'eau Flotille 3D observer & comprendre