1. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Update on validation of MERIS  w ’s at the BOUSSOLE site David Antoine 1, Constant Mazeran 2, Christophe Lerebourg 2, Ludovic Bourg 2, Marc Bouvet 3, Fabrizio D'Ortenzio 1, Samantha Lavender 4, Kathryn Barker 4, Bernard Gentili 1, Vincenzo Vellucci 1 1: Laboratoire d’Océanographie de Villefranche, Villefranche sur mer, France 2: ACRI-st, Sophia Antipolis, France 3: ESA-ESTEC, Noordwijk, The Netherlands 4: ARGANS Ltd, Plymouth, UK

2. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy A reminder about BOUSSOLE - Scientific objective: IOPs et AOPs documentation and understanding (bio- optics research), short-time changes... - Operational objective: vicarious radiometric calibration of ocean color satellite observations, and validation of the Level-2 geophysical products derived from these observations (e.g., chlorophyll, reflectances...). Motivation, objectives: establishing a long-term time series of optical properties (IOPs and AOPs), with two parallel objectives: Strategy: combination of 3 elements: - A Deep-sea mooring, for continuous collection of data at the surface - Monthly cruises for the buoy servicing and the collection of data complementary to the buoy data - An AERONET coastal station, to provide the necessary aerosol parameters

3. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy The BOUSSOLE site in the Ligurian Sea (northwestern Mediterranean)

4. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Waters at BOUSSOLE are permanently Case 1 waters Buoy data Morel & Maritorena, 2001 Upper limit for Case 1 waters Irradiance reflectance at 560 nm as a function of Chl

5. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy The range of bio-optical properties at BOUSSOLE is representative of global Case 1 waters Thick line : BOUSSOLE Thin line and thin dotted line : SeaWiFS global or Med Sea only Gray : NOMAD

6. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy The BOUSSOLE buoy, “transparent-to-swell” taut mooring

7. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Buoy data are in agreement with more “classical data”, i.e., profiling radiometer’s data Slope is 1 r 2 is 0.98 Bias is 8 10 -4 reflectance from a free-falling radiometer (Satlantic SPMR) reflectance from the buoy

8. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Status of buoy deployments - 5 years of deployment, with a quasi permanent data collection (September 2003  September 2008) - Over these 5 years (1825 days), we had 1560 days with a buoy at sea. This is a 85% “deployment success”, i.e., nearly operational - Over these 1560 days, 1300 were with data acquisition. This is a 83% “acquisition success”, which is also very satisfactory - Bi-monthly servicing since July of 2007 - No data from January 15 to June 15 2008 (5 months) - Next rotation is scheduled Jan 2009 - Evolution towards hyper-spectral measurements has started in June 2008 (350  800 nm, res 2 nm). Nominal set of 7- multispectral data is however preserved for continuity

9. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Matchup procedures Essentially follows: Bailey S.W., and P.J. Werdell, 2006: A multi-sensor approach for the on-orbit validation of ocean color satellite data products. Remote Sens. Environ., 102, 12-23. - 5x5 pixel box - Flags: glint, clouds, haze,  s <70°,  v <60°, clear sky - Spatial homogeneity is checked - MERIS: level-2 RR, last reprocessing  109 matchups - SeaWiFS: level-2 Merged Local Area Coverage (MLAC; until Dec. 2004) or Global Area Coverage (GAC; 2005-2006) data from reprocessing 5 (completed March 18, 2005)  193 matchups - MODIS-A: level-2 GAC data from reprocessing 1 (completed in February 2005)  185 matchups

10. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy 4-year time series of  w MERIS SeaWiFS MODIS-A Field data (10am – 2pm, clear sky)

11. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Full matchup set, using data from Sept 2003 to Dec 2007

12. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Statistics

13. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Matchup statistics, using data from Sept 2003 to Dec 2007 MERIS NrRPD|RPD|r2r2 myrmse 412391,5555,259,40,160,770,009850,01032 443981,2827,832,50,360,740,006810,00529 4901041,1414,018,70,450,780,004330,00289 5101031,1919,223,30,140,510,006150,00260 560981,1818,323,50,080,410,003780,00144 665652,32132,2133,10,00-0,080,001140,00069 681721,9494,595,90,200,690,000690,00063 All bands579 0,791,120,00078 SeaWiFS NrRPD|RPD|r2r2 myrmse 412610,94-5,720,60,400,700,003770,00449 4431911,021,916,20,470,710,004580,00310 4901930,96-3,513,20,340,560,005650,00244 5101930,93-6,914,00,110,350,006110,00194 5551080,91-9,016,90,090,410,002710,00122 6701790,95-5,253,80,000,110,000400,00034 All bands9250000,870,920,000300,00000 MODIS-A NrRPD|RPD|r2r2 myrmse 412590,93-7,124,10,530,780,002180,00437 4431800,98-2,016,70,560,770,002990,00305 4881850,93-7,214,10,450,620,004250,00255 5511820,91-9,315,90,220,590,001650,00105 6671830,85-15,344,10,030,220,000290,00028 All bands7890000,900,910,000180

14. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Conclusions - The requirements in terms of accuracy of the atmospheric correction are only met at 443 and 490 nm by the SeaWiFS and MODIS-A products. - The MERIS products don’t meet the requirements. - The water-leaving radiance reflectances provided by the three sensors at 412 nm are severely affected by atmospheric correction errors. - The uncertainty is significantly reduced for the “blue-to-green” reflectance ratio. - These results and the matchup statistics are in agreement with the results obtained by two other similar efforts carried out at a coastal site [Zibordi et al., 2006] and globally [Bailey and Werdell, 2006].  Vicarious calibration should be included in the MERIS L2 processing, as it is done for other OC sensors presently in orbit See next presentations

15. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Further information Antoine, D. M. Chami, H. Claustre, F. D’Ortenzio, A. Morel, G. Bécu, B. Gentili, F. Louis, J. Ras, E. Roussier, A.J. Scott, D. Tailliez, S. B. Hooker, P. Guevel, J.-F. Desté, C. Dempsey and D. Adams. 2006, BOUSSOLE : a joint CNRS-INSU, ESA, CNES and NASA Ocean Color Calibration And Validation Activity. NASA Technical memorandum N° 2006–214147, 61 pp. Antoine, D., P. Guevel, J.-F. Desté, G. Bécu, F. Louis, A.J. Scott and P. Bardey, 2008, The « BOUSSOLE » buoy – A new transparent-to-swell taut mooring dedicated to marine optics : design, tests and performance at sea, Journal of Atmospheric and Oceanic Technology, 25, 968-989. Antoine, D., F. D’Ortenzio, S.B. Hooker, G. Bécu, B. Gentili, D. Tailliez and A. Scott, 2008, Assessment of uncertainty in the ocean reflectance determined by three satellite ocean color sensors (MERIS, SeaWiFS, MODIS) at an offshore site in the Mediterranean Sea (BOUSSOLE project), Journal of Geophysical Research, 113, C07013, doi:10.1029/2007JC004472. Bailey S., S.B. Hooker, D. Antoine, J.P. Werdell and B. Franz, Vicarious calibration of ocean color satellite remote sensors: An analysis of sources and assumptions, Applied Optics, 47(12), 2035-2045.

16. 2nd MERIS/(A)ATSR User Workshop 22nd to 26th September 2008 ESA/ESRIN Frascati (Rome) Italy Thank you for your attention www.obs-vlfr.fr/Boussole