10ο Πανελλήνιο Συμπόσιο Ωκεανογραφίας & Αλιείας 7-11 Μαΐου 2012, Αθήνα Μεσόγειος Θάλασσα - Μαύρη Θάλασσα: Ένα ωκεανογραφικό «εργαστήριο»

1. Collecting and Assimilating Glider
Transects in the Levantine Sea
May-August ‘09 data show Cyprus Eddy
D. Hayes1, P. Testor2 , S. Dobricic3, G. Zodiatis1
1OceanographyCenter, University of Cyprus, Nicosia, Cyprus
2LOCEAN-IPSL/CNRS, Universite Pierre et Marie Curie, Paris, France
3INGV/CMCC, Bologna, Italy

2. 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

3. Glider description
• 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
Photo: A. Hannides

4. 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

5. Missions Accomplished
• Since March 2009, over 1930
dives (3860 profiles)
• Most to 1000 m

6. EYE of the Levantine
TS properties
• Depth-ave
velocity, Max
30 cm/s
• Anti-cyclonic
• Radius
~40km
• November
2009 to
January
2010
• Near
Eratosthenes
Seamount

7. 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)

8. 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)

9. EYE of the Levantine
Glider (Atalanta)
• 23 Nov-1 Dec 2009
• Salinity (top)
• Temperature (mid)
• Dissolved Oxygen (bot)
• Asymmetric: south
branch of core more
focused

10. EYE of the Levantine
Glider Comparisons with MS Merian
• 10 stations 4-5 Jan 2010
• Dives 170-250 7-31 Jan 2010 • 14-22 Jan 2010
• Depth-average currents from glider • Geostrophic Velocity (top) and
(1000m) and from ADCP (800m) ADCP (bottom)
0

12. OceanVar
Dobricic 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

13. 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

14. Results
• Numerical flow ―hindcast‖ simulation: Nov. 2009-April 2010
• Correction to T at 280 m
• Glider positions
• DAILY

15. Results
• EYE experiment assimilating only one glider‘s T, S profiles
• Sea surface elevation map at end of simulation: 19 April 2012
No assimilating Assimilating glider data
The difference

16. 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

17. 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

18. Work in Progress
Operational Data Assimilation—TODAY:
Glider mission and simulations: 16 December 2011 to present
Assimilated in CYCOFOS, compared to control run

19. Work in Progress
Operational Data Assimilation—TODAY:
Salinity at 360 m for control run (L) and D/A run (R) for this Wednesday
Need to quantify the improvement by comparing to independent data
E.G.: SST, XBT, SLA+MDT, cruise CTD/ADCP

20. Future Work
• New FP7 project, GROOM, has
started.
• Goal: to design a European Glider
Infrastructure.
• Heavily based on existing, but
integrated and improved.‘
• Recommend payloads, protocols,
operation centers, etc.
• Support policy AND research
• monitoring for parameter ‗X‘
• availability for process study ‗Y
Photo: TARA Oceans

21. 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