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10ο Πανελλήνιο Συμπόσιο Ωκεανογραφίας & Αλιείας 7-11 Μαΐου 2012, Αθήνα Μεσόγειος Θάλασσα - Μαύρη Θάλασσα: Ένα ωκεανογραφικό «εργαστήριο»
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Collecting and Assimilating Glider Transects in the Levantine Sea
D. Hayes1, P. Testor2 , S. Dobricic3, G. Zodiatis1
1Oceanography Center, University of Cyprus, Nicosia, Cyprus 2LOCEAN-IPSL/CNRS, Universite Pierre et Marie Curie, Paris, France3INGV/CMCC, Bologna, Italy
May-August ‘09 data show Cyprus Eddy
Goal: Accurate description of mean state----> Improve Forecast Accuracy• Method
• Collect high resolution temperature and salinity profiles over long periods in upper 1000 m (gliders)
• Implement glider data assimilation (3DVAR) in operational regional model (CYCOFOS)
• Results:
• Cyprus eddy + Atlantic Water always found (>3/2009 with gliders)
• Assimilation run shows difference from the control run
• Analysis:
• Cyprus Eddy dominates a complex circulation
• Work needed to quantify improvement in forecast
• Conclusions:
• RT glider observations gliders unique: improve ocean forecasts
• Battery-powered, buoyancy-driven
• 25-50 cm/s, 16-45o slope
• CTD, oxygen, fluorescence, optical backscatter, currents
• surface transmit/receive for data and instructions every 5h.
• 1000 m dive capability
Glider description
Photo: A. Hannides
Seaglider description• Low-drag fairing over hull of compressibility ~= seawater
• Lithium batteries, ~6 mo life (4600 km or 650 dives to 1km)
• Iridium satellite phone for data, instruction transfer
• Controlled with file exchange (commands, waypoints, configuration)
Photo: U of Washington
Missions Accomplished• Since March 2009, over 1930
dives (3860 profiles)
• Most to 1000 m
EYE of the LevantineTS properties
• Depth-ave velocity, Max 30 cm/s
• Anti-cyclonic• Radius
~40km• November
2009 to January 2010
• Near Eratosthenes Seamount
EYE of the Levantine (12/2009)• Sampling the warm core Cyprus Eddy• Labs: LOCEAN, LOV (fr), OGS (it), ULB (be), UCY-OC (cy)• Gliders: physical and biogeochemical context for shipborne
measurements
– 6 gliders deployed from Limassol
– 2 profiling floats– 4 surface drifters– shipborne
measurements by CYBO (Cyprus), TARA (French), Merian (German)
EYE of the Levantine (12/2009)• Sampling the warm core Cyprus Eddy• Labs: LOCEAN, LOV (fr), OGS (it), ULB (be), UCY-OC (cy)• Gliders: physical and biogeochemical context for shipborne
measurements
– 6 gliders deployed from Limassol
– 2 profiling floats– 4 surface drifters– shipborne
measurements by CYBO (Cyprus), TARA (French), Merian (German)
• 23 Nov-1 Dec 2009• Salinity (top)• Temperature (mid)• Dissolved Oxygen (bot)• Asymmetric: south
branch of core more focused
EYE of the LevantineGlider (Atalanta)
• 10 stations 4-5 Jan 2010• Dives 170-250 7-31 Jan 2010• Depth-average currents from glider
(1000m) and from ADCP (800m)
0
EYE of the LevantineGlider Comparisons with MS Merian
• 14-22 Jan 2010• Geostrophic Velocity (top) and
ADCP (bottom)
OceanVarDobricic and Pinardi, 2008
• Calculates T and S residuals (model “background” minus observations) at every time step data are present
• After POM, calculates “correction” T and S based on residuals in window (1.5d)
• Applies corrections at the beginning of the next run (20 time steps).
Glider (red) and model (blue) S,T profiles
Difference (black) and correction (green)
8 Dec 2009
Results• Numerical flow “hindcast” simulation: Nov. 2009-April 2010
• Daily update of surface forcing and open boundary conditions
• Quantify the value of 1 glider, vs 6 gliders, vs floats+ships+gliders
• EYE experiment (so far only 0 and 1 completed)
Corrections on S and T at 300 m
8 Dec 2009
Results• Numerical flow “hindcast” simulation: Nov. 2009-April 2010
• Correction to T at 280 m
• Glider positions
• DAILY
Results• EYE experiment assimilating only one glider’s T, S profiles
• Sea surface elevation map at end of simulation: 19 April 2012
Assimilating glider dataNo assimilating
The difference
Discussion• Quantify the value of 1 glider, vs 6 gliders, vs floats+ships+gliders
• EYE experiment (so far only 0 and 1 completed—see difference below)
• See problem at BC
Discussion• Quantify the value of 1 glider, vs 6 gliders, vs floats+ships+gliders
• EYE experiment (so far only 0 and 1 completed—see difference below)
• See problem at BC
Work in ProgressOperational Data Assimilation—TODAY:
Glider mission and simulations: 16 December 2011 to presentAssimilated in CYCOFOS, compared to control run
Work in ProgressOperational Data Assimilation—TODAY:
Salinity at 360 m for control run (L) and D/A run (R) for this WednesdayNeed to quantify the improvement by comparing to independent data
E.G.: SST, XBT, SLA+MDT, cruise CTD/ADCP
Future Work• New FP7 project, GROOM, has
started.
• Goal: to design a European Glider Infrastructure.
• Heavily based on existing, but integrated and improved.’
Photo: TARA Oceans
• Recommend payloads, protocols, operation centers, etc.
• Support policy AND research
• monitoring for parameter ‘X’
• availability for process study ‘Y
Conclusions
• Gliders improve forecasting skill
• Quantifying the improvement is not done yet
• Eastern Levantine highly variable and full of mesoscale: need real time data
Acknowledgements• Funding: FP7-ECOOP, FP7-GROOM,
Cyprus RPF and UCY, TARA/Oceans.
• Colleagues: MFS, U of Athens (ALERMO and Skiron providers)
• Launch/recovery support: Department of Fisheries and Marine Research Photo: A. Hannides