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The GlobCOLOUR Products Gilbert Barrot ACRI-ST

The GlobCOLOUR Products Gilbert Barrot ACRI-ST. Globcolour / Medspiration user consultation, Dec 4-6, 2006, Villefranche/mer. The GlobCOLOUR products The products The spatial and temporal coverages and the merging methods The variables. The GlobCOLOUR products The products

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The GlobCOLOUR Products Gilbert Barrot ACRI-ST

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  1. The GlobCOLOUR ProductsGilbert BarrotACRI-ST Globcolour / Medspiration user consultation, Dec 4-6, 2006, Villefranche/mer

  2. The GlobCOLOUR products The products The spatial and temporal coverages and the merging methods The variables

  3. The GlobCOLOUR products The products The spatial and temporal coverages and the merging methods The variables

  4. The products • Chlorophyll-a concentration (Chla) • Diffuse attenuation coefficient (in-water) (Kd) • Fully normalised water leaving radiances (available bands) • Coloured dissolved and detrital organic materials (CDM) • Total suspended matter (TSM) or particulate backscattering coefficient (bbp) • Aerosol optical thickness (AOT@865nm) • Data quality flags • Cloud fraction • Excess of radiance at ~ 555 nm (turbidity index) (EL555) • Error estimates per pixel for each layer +flags

  5. Not all parameters are available for all merging methods

  6. CHL1 July 2002 Weighted average Weighted average pre-processing Inverse formulation is available in the Product User Guide

  7. CHL1 July 2002 GSM Single-instrument daily L3 fully normalised water leaving radiances [1] are used by the GSM model. These radiances are not inter-calibrated before ingestion in the model. CHL1 is one of the model outputs. [1] MERIS: 412 nm, 443 nm, 490 nm, 510 nm, 560 nm MODIS: 412 nm, 443 nm, 488 nm, 531 nm, 551 nm SeaWiFS: 412 nm, 443 nm, 490 nm, 510 nm, 555 nm

  8. CDM July 2002 GSM CDM is the coloured dissolved and detrital organic materials (m-1). Two GlobCOLOUR products are generated for PPS: MERIS-derived CDM product GSM-derived CDM product The merged CDM concentration is generated using the GSM model from the daily L3 radiance products.

  9. Bbp July 2002 GSM bbp is the particulate back-scattering coefficient (in m-1) at λ0 = 443nm. The merged bbp concentration is generated using the GSM model. From the initial GlobCOLOUR bbp merged product, we have therefore the possibility of generating the following products: bp (m-1) = bbp/0.015 TSM (g.m-3) = 1.73*bp = 1.73*bbp/0.015

  10. Kd(490) is the diffuse attenuation coefficient at 490 nm (m-1). It is one indicator of the turbidity of the water column. The merged Kd(490) is computed directly from the merged CHL1, using the following equation: with: Kw(490) = 0.0166 m-1 = 0.08349 e(490) = 0.63303 Kd(490) July 2002 From AVW CHL1 (Morel, 2006)

  11. L443 July 2002 Weighted average Lxxx is the fully normalised water leaving radiances at xxx nm (in mW/cm²/µm/sr). Spectral values are: 412, 443, 490, 510, 531, 550-565, 620, 665-670, 681 and 709 nm. MERIS reflectances (L2 products) are converted into fully normalised water leaving radiances (normalisation is not applied to the MERIS 681 nm fluorescence band and to the 709 nm band.). MODIS-only - MERIS-only - Preprocessing

  12. L555 July 2002 Weighted average The 550-565 bands are submitted to a specific processing just before averaging to prepare a more consistent merging between the instruments. First of all, all bands are spectrally re-affected to 555 nm, using a inter-spectral conversion LUT which is a function of the CHL1 concentration.

  13. EL555 July 2002 From AVW L555 and CHL EL555 is the relative (%) excess of radiance at 555 nm, above a given threshold. The EL555 parameter is computed from the L555 fully normalised water leaving radiance and the CHL1 products. The daily products are computed for each instrument using the associated daily water leaving radiance and daily CHL1, while the merged product is computed from the merged L555 and the merged CHL1 concentration. Details in User Guide

  14. CF July 2002 CF is the cloud fraction (expressed in %). daily products: percentage of input pixels per bin flagged as cloudy in the original level 2 products 8-days and monthly products: percentage of merged days per bin where the daily cloud fraction is greater than a specified threshold (50% in current processor conf.)

  15. The flags

  16. The GlobCOLOUR products The parameters The spatial and temporal coverages and the merging methods The variables

  17. The spatial and temporal coverage The merging techniques • Global Earth domain (PPS / FPS or Global ) • Specific Diagnostic Data Set sites (100x100 km2) (DDS or Local ) • Simple averaging • Weighted averaging • GSM method • Daily merged • 8-days • Monthly • ISIN • Plate-Carré

  18. GlobCOLOUR products content Complete details are available in the GlobCOLOUR Product User Guide Information stored in the products (1): stdev is not computed in the nearest neighbour interpolation process (2): before merging step, error is not provided pixel-wise, but the global relative error (%) coming from the characterisation is saved in metadata (3): stdev is not defined at the output of the merging module. Only error is estimated. (4): error is the output of the weighted average merging model. Only products merged using this method contain the error pixel-wise field; other products does not contain this field. (5): for merged daily, 8-days and monthly products, count is not the number of L2 binned pixels, but the number of days contributing to the bin. So for merged daily products, it is always set to 1. (6): computed from the quadratic sum of the inverse errors of the parents products. (7): quicklook product does not contain any geophysical variable

  19. The GlobCOLOUR products The products The spatial and temporal coverages and the merging methods The variables

  20. Global level-3 binned products GlobCOLOUR products contain: - Geolocation information - Product values (mean, stdev, error) - Binning information (weight, count) - Flags - Metadatas Variables are stored as 1D vectors for ISIN gridsand maps for PC grids

  21. Global level-3 binned products Tools to browse/plot ISIN and PC products are available on the GlobCOLOUR web site and any external tools using netCDF reader and ISIN / PC grid definition

  22. Global level-3 binned products Main characteristics of the global ISIN grid The full definition of the global ISIN grid is detailed in the Product User Guide

  23. Global level-3 binned products • The row(), col(), center_lat(), center_lon() and lon_step() arrays allow an easier conversion of the bin index into geographical coordinates. • Equations to compute center longitude and latitude for a bin b: • index = row(b) – first_row (first_row is a global attribute) • lat(b) = center_lat( index ) • lon(b) = center_lon( index ) + col(b) * lon_step( index )

  24. Thank you for your attention Data access: www.globcolour.info Helpdesk Service@globcolour.info

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