Linking MERIS Validation at Sagres, SW Portugal with Validation of OLCI and SLSTR Sensors on Sentinel -3
Icely, John¹; Moore, Gerald²; Cristina, Sonia¹; Goela, Priscila¹; Newton, Alice^3
1Sagremarisco Lda/ CIMA, U. of Algarve, PORTUGAL; ²Bio-Optika, UNITED KINGDOM; ³CIMA, U. of Algarve / CEE-NILU, Norway, NORWAY

Three Stations at 2, 10 and 18 Km off the SW coast of Portugal have provided in situ data for the validation of the MERIS (Medium Resolution Imaging Spectrometer) sensor on the ESA ENVISAT satellite since 2008 and its demise in 2012. Station A (37A°00'34''N 8A°54'07''W), Station B (36A°55'53''N 8A°53'40''W), Station C (36º50'32''N 8º54'54''W) allow for comparisons between near-shore and off-shore conditions. The clear skies and flexible access to boats at Sagres have enabled approximately 300 matches between MERIS products and in situ data. The objective of the Sagres Validation Ocean Colour Portugal (SagValOCPort) proposal is to link validation of MERIS products with validation of products obtained from OLCI (Ocean Land Colour Instrument) and SLSTR (Sea and Land Surface Temperature ) on Sentinel 3. The aim is to collect in situ measurements within 0.5 and 1.5h of the overpasses by Sentinel-3 for the coastal Station A, and for the more offshore Stations B and C, respectively. The in situ data under consideration for this validation effort are: geo- located remote sensing reflectances at the centre wave lengths closest to 413, 443, 490, 510, 560, 620, 665, 681, 709, 779 , 870 and 1000 nm; aerosol optical thickness at 413, 443, 490, 510, 560, 620, 665, 870 and 1000 nm; angstrom exponent; water vapour; spectral diffuse coefficient Kd(490)(m-1); transparency (m-1); depth (m) at surface, 0.5 Secchi depth, and Secchi depth; Algal Pigment 1 (Aµg.l-1);Algal Pigment 2 (Aµg.l-1) ; total suspended matter (mg.l-1); absorption coefficients at 443 and nm for phytoplankton aph (m-1); absorption coefficients at 443 nm for non-algal particles anap (m-1); absorption coefficients at 443 nm for yellow substances ays (m-1); sea surface temperature. Ancillary data will include date, time, latitude, longitude, wind speed and atmospheric pressure, as well as nutrient data, analyses of the phytoplankton community and CTD profiles of the water column for temperature, salinity and photosynthetic active radiation. This in situ data will be used to validate the OLCI products: OL_1_EFR - Level 1 full resolution; OL_1_ERR - Level 1 reduced resolution; OL_2_WFR - full resolution water products including reflectances and OL_2_WRR - reduced resolution water products including reflectances. This data will also validate the Sea and Land Surface Temperature Radiometer (SLSTR) product SL_2_WST-single product SST. Finally, data from the AERONET (AErosol RObotic NETwork) station will be used for the validation of merged data from OLCI and SLSTR (Synergy) for the product SY_2_SYN. The systematic and random differences between the in situ data and Sentinel-3 products will be presented in tabular and graphical form (histograms and scatter plots) with scientific interpretation of the results using the appropriate statistical analyses.. All accepted measurements for validation will be submitted to the ESA data repository for Sentinel-3, equivalent to the MERMAID (Matchup in-situ Database) data base for MERIS products. In order to provide continuity between ENVISAT and Sentinel-3 there is a current effort to continue with at least some of the in situ measurements at Sagres that will be required for OLCI and SLSTR validation. This validation would also contribute to the other activities of the Ocean Colour Portugal Consortium.