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 (case I water).

• 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

• Contribute to reprocessing SeaWiFS dataset using the selected Mediterranean algorithm

• Prepare Mediterranean gridded data compatible with model requirements.

ISAC Contribution to Ocean Color activity

Comparison of different ocean colour sensors and development of inter-calibration and merging techniques

• Contribute to the definition of the suitable intercaliblation and merging tecnique for OC data

• Identificatify the characteristic time/space scales of the chlorophyll field in the Mediterranean Sea

• Develop an appropriate method to produce daily fields of ocean colour parameters for data assimilation for Mediterranean Sea.

• Define an optimal interpolation algorithm that takes in to account the different characteristics of ocean colour retrieval in case I/case II waters.

• Validate SeaWiFS, Polder, MODIS, MERIS chlorophyll products as well as merged binned data produced by Mersea ageist in situ observation

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.

Validation of SeaWiFS ocean color algorithms in the

Mediterranean Sea

ENEA -CR Casaccia – Sezione Modellistica Oceanografica

Stazione Zoolologica ‘A. Dohrn’ Laboratorio di Oceanografia Biologica 3

2

1

Validation of Chlorophyll estimated by SeaWiFS against in situ Chlorophyll and bio-optical measurements

in situ bio-optical measurements and concurrent in situ chlorophyll-a data

Sat

elli

te g

eop

hys

ical

par

amet

er r

etri

eval

an

d v

alid

atio

n

SeaWiFS chlorophyll-a estimates validation against concurrent in situ chlorophyll-a

From D’Ortenzio et al., Rem. Sens. Env, 2002

A regional algorithm is required

%116% E%73% E

Validation of Chlorophyll estimated by SeaWiFS against in situ Chlorophyll measurements:

Crosses; SATLANTIC band-ratio vs. in situ chlorophyll.

Dashed line: NASA OC4V4 algorithm

Continuous lines: L-DORMA and NL-DORMA.

Sat

elli

te g

eop

hys

ical

par

amet

er r

etri

eval

an

d v

alid

atio

n

Scatter plot NL-DORMA versus concurrent in situ chlorophyll-a data

From D’Ortenzio et al., Rem. Sens. Env, 2002

%08.0% E

Applicazione del DORMA alle immagini di clorofilla

Validation of empirical SeaWiFS algorithms for chlorophyll-a retrieval in the Mediterranean Sea: a case study for oligotrophic seas

By

Fabrizio D’Ortenzio, Salvatore Marullo, Maria Ragni, Maurizio Ribera d’Alcalà, Rosalia Santoleri

Remote Sensing of the Environment , 2002

DORMA Algorithm based on 1998-2000 data

New data from 2000 to 2003: an independent data-set

Validation of DORMA, Bricout and MERIS algorithms for the Mediterranean Sea

Bio-optical measurements: (103 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: (> 800 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 where made in framework of Italian National Projects

AVHRR, SeaWiFS

The NRT satellite observing system for the Adriatic sea

The satellite OC observing system ADRICOSM experience

In the framework of ADRICOSM Project ISAC developed the first OC observing system that provides NRT ocean color data for modeling data assimilation

This system is operative since October 2002 and provides SeaWiFS images in RT and data on the model grid in NRT of the Adriatic Sea.

Ocean Color daily products for the Adriatic Sea

01011001 NRT chlorophyll data (SeaWiFS) on AREG model grid

gif images of chlorophyll at 1 km resolution

gif images of case I / case II / clouds masks

http://gos.ifa.rm.cnr.it/adricosm