Development of ocean color algorithms in the Mediterranean Sea Rosalia Santoleri 1,, Gianluca Volpe...
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Transcript of Development of ocean color algorithms in the Mediterranean Sea Rosalia Santoleri 1,, Gianluca Volpe...
Development of ocean color algorithms in the Mediterranean Sea
Rosalia Santoleri1,, Gianluca Volpe 1, Simone Colella1,3,
Salvatore Marullo2, Maurizio Ribera D’Alcalà3, Vincenzo Vellucci3
ENEA -CR Casaccia – Sezione Modellistica Oceanografica
Stazione Zoolologica ‘A. Dohrn’ Laboratorio di Oceanografia Biologica 3
2
1
ISAC Contribution to Ocean Color activity
Mediterranean high resolution surface chlorophyll mapping
• Use available bio-optical data sets to estimate the uncertainties of the existing ocean colour algorithms and to define an optimal chlorophyll algorithm for the Mediterranean Sea.
• Adapt the OC processing software to include selected regional algorithms and validate satellite chlorophyll estimates on the basis of in situ data.
• Evaluate the uncertainties of all current global satellite chlorophyll products available from public archive (e.g. DAAC) in the Mediterranean
• Reprocessing SeaWiFS dataset using the selected Mediterranean algorithm
• Prepare Mediterranean gridded data compatible with model requirements.
Why Mediterranean needs regional algorithm ?
Chlorophyll concentrations over the oligotrophic waters of the Mediterranean Sea are systematically overestimated when global algorithms (e.g. OC4v4) are used to convert blue-to-green reflectance ratios in to chlorophyll-a concentrations:
•Gitelson et al. (Journal of Marine System, 1996)
•D’Ortenzio et al. (SIMBIOS meeting January 2001)
•D’Ortenzio et al. (Remote sensing of the Environment, 2002)
•Bricaud et al . (Remote sensing of the Environment, 2002)
•Claustre et al. (Geoph. Res. Letters, 2002)
From these works it results that global algorithms cannot be applied to-court to the Mediterranean Sea but a specific cal/val activity is needed.
Bio-optical measurements: (143 chl/opt measurement points) to define the Mediterranean regional algorithm
• In water downwelling irradiance and upwelling radiance profiles using SATLANTIC SPMR• above water measurements using the SIMBAD and SIMBADA radiometer • In the bio-optical stations phytoplankton pigments distribution (HPLC and spectro-fluorometric
analysis) and ancillary biological data were also acquired following NASA protocols.
In situ chlorophyll-a data: (872 chl profiles) to validate SeaWiFS, Polder, MODIS, MERIS chlorophyll products and merged level 3 binned data produced by Mersea
Mediterranean Ocean Color CAL/VAL DATA SETS
10 Mediterranean cruises from 1998 up to now were organized by ISAC in the framework of Italian National Projects
Bio-optical stations
Cruise Period Zone# of
profiles
Chlorophyll Range# of
Satlantic# of
SIMBAD(A)
MIN MAX
MATER 425/4/199815/5/1998
Sardinia ChannelSicily Channel
57 0.025 0.105 - -
MATER 520/10/199827/10/1998
Sicily Channel 50 0.047 0.085 - -
EMTEC 9920/4/19997/5/1999
Ionian Sea 125 0.039 0.137 20 -
MATER 614/5/199930/5/1999
Sardinia ChannelSicily Channel
100 0.003 0.135 - -
PROSOPE04/09/199914/10/1999
Western BasinIonian Sea
16 0.020 0.112 16 -
SYMPLEX 9921/10/19996/11/1999
Sicily ChannelIonian Sea
212 0.039 0.176 12 -
NORBAL 126/3/200019/4/2000
Gulf of Lions 81 0.113 2.289 - -
NORBAL 25/12/2001
20/12/2001Gulf of Lions
Tyrrhenian Sea65 0.088 0.386 13 14
NORBAL 46/3/2003
26/3/2003Gulf of Lions 115 0.428 7.061 16 28
NORBAL 518/4/200325/4/2003
Gulf of Lions 40 0.605 2.096 4 7
DINA*29/3/200128/8/2001
Gulf of Naples 11 0.079 0.455 11 -
DYFAMED*5/2/1998
25/11/2002Liguro-Provencal 55 0.042 2.366 - -
All cruises 1998-2003 Mediterranean 872 0.003 7.06192 49
141
Validation of Ocean Color Algorithms
)( 44
33
221010 RaRaRaRaaC
4)( 3
32
21010 cC RcRcRcc
1)/( 5554430dRRdC
OC4v4: R is log10 of either the 443/555 or the 490/555 or the 510/555 band reflectance ratios, depending on its value (the maximum is chosen)
D’Ortenzio et al. 2002 (DORMA): R is log10 of the 490/555 band reflectance ratios.
Bricaud et al. 2002: R is log10 of the 443/555 band reflectance ratios for Chl<0.2 (OC4v4 is used in the other cases)
REGIONAL
GLOBAL
)( 44
33
221010 RbRbRbRbbC
MEDOC4 : R is log10 of either the 443/560 or the 490/555 or the 510/555 band reflectance ratios. The switch from one band ratio to another one is based on the chlorophyll concentration itself (the Maximum is Chosen)
NEW MEDITERRANEAN ALGORITHM
SeaWiFS data validation
A Match-up dataset between concurrent SeaWiFS data and in situ measurements has been contructed
1. SeaWiFS L1A passes corresponding to in situ observation were selected
2. The regional algorithms (DORMA, Bricout et al, and the new MED OC4) were inserted in the SeaDAS Code
3. SeaWiFS L1A passes were processed using the different algorithms:OC4v4, DORMA, Bricout, MEDOC4
4. A Match-up dataset is contructed.
Map of the Satellite-in situ match-up stations
Merging OC data in the MED
• Define the error of global OC color products at regional scale and define a strategy to take into account the regional optical properties of the MED in the Merging procedure
• Define of the suitable intercalibration and merging tecnique for OC
• Define an optimal interpolation algorithm that takes in to account the different characteristics of ocean colour retrieval in case I/case II waters.
10 March 2003
25 March 2003
Primary production in the Mediterranean Sea from remote
sensing data: a model adaptation
Depth
(m
)
CHL (mg m-3)
Depth
(m
)
CHL (mg m-3)
WEST MED: 172 gc m-2 y-1
EST MED: 123 gc m-2 y-1Bosc et al.,2003
Antoine et al.,1995WEST MED: 197 gc m-2 y-1
EST MED: 137 gc m-2 y-1
In situ C14 Method EST MED: 55-97 gc m-2 y-1
WEST MED: 78-150 gc m-2 y-1
Remote Sensed data of pigment
concentration
Trophic States e Morel and Berthon’s (1989) Correlations
Primary Production Maps
Morel and Berthon carried out relationships between Ctot vs Cpd and Ctot vs Csat. Cpd is defined as the mean pigment concentration in a layer named penetration depth Zpd=1/k where k is the attenuation coefficient for the downwelling PAR irradiance:
Zpd can be estimated from Ze on the base of the relation: Zpd=Ze/4.6 .Instead, Csat is defined as the weighted mean pigment concentration in
the layer Zpd:
Csat is very similar to the Optically Weighted Pigment (OWP) concentration considered as the best representation of what satellite sensors can measurement.
pd
Z
0pd Z
dz C(z)C
pd
pd
pd
Z
0
Z
0sat
dz exp(-2kz)
dz exp(-2kz) C(z)C
In situ bio-optical data has been used to verify the relationship between the euphotic depth (Ze) and total pigment concetration insite this layer.Ze: depth where the PAR (Photosynthetic Active Radiation) become 1% of the surface value
Ctot=54.679 Cpd
0.6532 Ctot=48.13 Csat0.627≠
Ctot=40.6 Cpd0.46 Ctot=40.6 Csat
0.459=