Laboratorio Analisi & Integrazione Dati Satellitari Oceanografici
Referente: Dr. Salvatore Marullo
Tel: +39-06-9400 5867
Ocean Color: bio-optical algorithms for Chlorophyll
Fig. 1. (a) Relation between "in situ" MBR and CM used to derive the new coefficients for the MedOC4 algorithm.
Different optical data sources are highlighted with different colours and symbols. MedOC4 functional form is superimposed.
(b) MedOC4-derived chlorophyll versus CM. The 1:1 (continuous line) 1:2 (bottom dashed line) and 2:1 (top dashed line) lines
are also plotted. From Volpe et al. 2007
The quantification of the spatial and time variability of phytoplankton biomass and biological
activity is among the main scopes of ocean color observation missions.
Starting from the beginning of this millennium field activity and ocean
color data analysis in The Mediterranean Sea raised the question of why the global
algorithms overestimate chlorophyll-a concentration in the Mediterranean Sea.
In fact the analysis of bio-optical measurements revealed a systematic overestimation
of chlorophyll-a concentration by NASA global algorithms. For this reason,
we introduced a new algorithm, retrieved by fitting a Mediterranean bio-optical
data set with an OC2-like functional forms. The DORMA (D'ORtenzio - MARullo)
algorithm was the result of this first attempt (D'Ortenzio et. al., 2002).
This first algorithm was refined in the following years using a larger set of
in situ bio-optical measurements (Volpe et al., 2007) producing the MedOC4 (Fig. 1).
This activity was conducted in the framework of the NASA SYMPLEX project (Synoptic Mesoscale Plankton Experiment)
also funded by ASI in collaboration with the GOS group of ISAC-CNR.
Ocean Color: Coastal Oceanography
Ocean Color application for coastal oceanography have been developed in the framework of the
ADRICOSM NERES and ADRICOSM STAR projects. The objective was to study of the impact of the
river outflow and the evolution of the estuarine area on the marine environment in the areas
of the Neretva river (fig. 2) and Montenegro Coastal area (Fig. 3).
Further developments of this activity will be done in the framework of an incoming project
founded by the Italian Space Agency (CoastSat). A new proposal to develop a procedure to
estimate the Phytoplankton Size Classes (PSC) distribution from satellite ocean color data
will be submitted to EU by the end of this year (2010).
Oil Spill detection:
ENEA participates to the Italian Space Agency project PRIMI (PRogetto pilota Inquinamento Marino da Idrocarburi)
contributing to forecast and analysis of the Tyrrhenian Sea Circulation (UTMEA Section of ENEA) and to the
field activity (PRIMI cruise August 2009) with lidar measurements to detect oil spills observed by satellite.
Sea Surface Temperature and diurnal cycle:
The increasing quality of Sea Surface Temperature derived from satellite measurements has now reached
such levels that its diurnal cycle cannot be considered any more as geophysical noise.
The knowledge of the SST diurnal cycle contribute to all those ocean applications that include
air-sea interaction processes and is important for assimilation in ocean forecasting schemas either
when the model do not fully include the physics of the daily temperature variation of the upper warm-layer
or when this variability is requested with enough precision to reproduce usual to extreme diurnal warming events.
Moreover, if the foundation SST (i.e. the temperature at the base of the diurnal thermocline) is the ideal measure to
construct consistent time series of regional to global SST maps for climate time series, it is necessary to estimate
diurnal warming at the ocean surface and remove it from daytime SST retrievals. This will contribute to reduce the
geophysical noise due to the diurnal cycle and the bias due to the uneven distribution of the valid SST retrieval during the day.
We participate to the GHRSST-PP Diurnal Variability Working Group (DVWG) of GHRSST (Group for High-Resolution Sea Surface Temperature)
and to European Research Network for Estimation from Space of Surface Temperature (ERNESST).
Our goal is to develop a new approach that combine high time frequency satellite data, mainly from geostationary
satellites but non only, and MyOcean Operational Ocean Forecasting Models products to generate level 4 hourly maps
of sea surface temperature resolving the diurnal variations and including extreme diurnal warming events.
Preliminary results are already available (see fig. 4).
Fig 2. . Interannual variability of the monthly aCDOM(300 nm) in the Neretva area
Fig 3. Ocean Color parameters derived from SeaWiFs off of the Montenegro coasts (March 4th 2004)
Fig. 4. SST reconstruction of a diurnal warming event in the Mediterranean Sea.
The method uses SEVIRI SST data as input of an adapted optimal interpolation schema
that also uses ocean general circulation model (OGCM) analysis (OPA) as first guess.
- Measuring the oceans from space: the principles and methods of satellite oceanography, Ian Stuart Robinson, Springer, 2004 - 669 pages
- Oceanography from Space, Vittorio Barale, Springer, 2010 - 374 pagine
- Validation of empirical SeaWiFS algorithms for chlorophyll-a retrieval in the Mediterranean Sea A case study for oligotrophic seas, D'Ortenzio et al. Remote Sensing of Environment 82 (2002) 79-94, 2002