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1The GlobCOLOUR products - 1
The GlobCOLOUR Products
Gilbert BarrotACRI-ST
Globcolour / Medspiration user consultation, Dec 4-6, 2006, Villefranche/mer
2The GlobCOLOUR products - 2
The GlobCOLOURproducts
The products
The spatial and temporal coverages and the merging methods
The variables
3The GlobCOLOUR products - 3
The GlobCOLOURproducts
The products
The spatial and temporal coverages and the merging methods
The variables
4The GlobCOLOUR products - 4
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
The products
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Not all parametersare available for
all merging methods
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CHL1July 2002Weighted average
Weighted average pre-processing
Inverse formulation is available in the Product User Guide
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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 nmMODIS: 412 nm, 443 nm, 488 nm, 531 nm, 551 nmSeaWiFS: 412 nm, 443 nm, 490 nm, 510 nm, 555 nm
CHL1July 2002
GSM
8The GlobCOLOUR products - 8
CDMJuly 2002
GSM
CDM is the coloured dissolved and detrital organic materials (m-1). Two GlobCOLOUR products are generated for PPS:
MERIS-derived CDM productGSM-derived CDM product
The merged CDM concentration is generated using the GSM model from the daily L3 radiance products.
9The GlobCOLOUR products - 9
Bbp
July 2002GSM
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
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Kd(490)July 2002
From AVW CHL1
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
)(ewd chl)()(K)(K
490(Morel, 2006)
11The GlobCOLOUR products - 11
L443July 2002Weighted 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
12The GlobCOLOUR products - 12
L555July 2002Weighted average
The 550-565 bands are submitted to a specific processing just before averagingto prepare a more consistent merging between the instruments.First of all, all bands are spectrally re-affected to 555 nm, using a inter-spectralconversion LUT which is a function of the CHL1 concentration.
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EL555July 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 dailywater leaving radiance and daily CHL1, while the merged product is computedfrom the merged L555 and the merged CHL1 concentration.
Details in User Guide
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CFJuly 2002
CF is the cloud fraction (expressed in %).
daily products: percentage of input pixels per bin flagged as cloudy in the originallevel 2 products
8-days and monthly products: percentage of merged days per bin where the daily cloudfraction is greater than a specified threshold (50% in current processor conf.)
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The flags
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The GlobCOLOURproducts
The parameters
The spatial and temporal coverages and the merging methods
The variables
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Global Earth domain (PPS / FPS or Global ) Specific Diagnostic Data Set sites (100x100 km2) (DDS or Local )
The spatial and temporal coverageThe merging techniques
Simple averaging Weighted averaging GSM method
Daily merged 8-days Monthly
ISIN Plate-Carré
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GlobCOLOUR products content
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
Complete details are available in the GlobCOLOUR
Product User Guide
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The GlobCOLOURproducts
The products
The spatial and temporal coverages and the merging methods
The variables
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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
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Global level-3 binned products
and any external tools using netCDF reader and ISIN / PC grid definition
Tools to browse/plot ISIN and PC products
are available on the GlobCOLOUR web site
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Main characteristics of the global ISIN grid
The full definition of the global ISIN grid isdetailed in the Product User Guide
Global level-3 binned products
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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 )
