ISRO
AO OCM-2; 14 March 2008
Application of satellite technology for characterizing
seasonal behaviour of sea pigment concentration in
the West Indian Ocean and analyzing its relationship
with environmental parameters
- STIOS P.I. Giovanni Laneve
IIA
Italian National Research Council
Institute of Atmospheric Pollution
E-mail: [email protected]
Università degli Studi di Roma
“La Sapienza”, CRSPM
E-mail: [email protected]
Workshop OCEANSAT 2; Rome June 25, 2009
Italian National Research Council
Institute of Methodologies for
Environmental Analysis
E-mail: [email protected]
Project Theme:
The proposal falls in the following broad category:
•
Synergistic studies using multi-sensor data to understand
processes.
More specifically, the proposal cover the following areas of interest:

Validation of OCM derived geophysical parameters

Inter-sensor data comparison and data merging

Algal bloom detection

Ocean color and sustainable fisheries management

Synergistic use of ocean color and scatterometer winds
Page  2
Outline
This proposal aims at studying the seasonal characteristics of the West
Indian Ocean from the point of view of the water parameters, and circulation
conditions.
This purpose will be achieved by combining water quality data from OCM-2
sensor, sea surface temperature information from MODIS sensor and wind
data from Oceansat-2 Scatterometer.
This seasonal behaviour will be compared with results obtained by using
data acquired in the past or simultaneously on the same region by using
different sensors (SeaWiFS, MODIS).
Page  3
Western Indian Ocean (WIO) area of interest.
Page  4
The acquisition circle of the BSC ground station (-2.99° S. lat. and 40.19° E.
long.) in yellow
(CRPSM) Profile
Remote Sensing
Station (RSC) - BSC
6m antenna in X band of the
RSC station.
Acquisition circle of the RSC station for a
Remote Sensing satellite.
10-m antenna operating in S,X,L
bands of the TT&C station.
2 m antenna L-band of the
RSC station.
Page  5
30 April - 2 May, 2008 Maracaibo (Venezuela)
Western Indian Ocean (WIO)
WIO has been described as a biological ‘desert’ for its very low nutrient
levels and its impoverishment in upwelling systems.
There is no doubt that overall it is an oligotrophic region where the average
monthly chlorophyll concentration is found between a minimum of 0.1
mg/m3 and a maximum of 0.3 mg/m3. Even though from previous studies
results that it presents some notable exceptions such as the periods around
August and January.
Page  6
Southeast Monsoon (May-August)
Page  7
Northeast Monsoon (October-April)
2
1
3
5
3
Chla monthly
mean content [mg/m
]
Chla mounthly mean
content
mg/l
4
0.9
0.9
Area 1
Area 1
0.8
0.8
Area 2
Area 2
0.6
0.6
Area 3
Area 3
0.4
0.4
Area 4
Area 4
0.2
0.2
Area 5
Area5
Page  8
1
2
3
4
5
6
7
Time [month]
8
9
10
11
12
“Kusi” South-East wind
regime produces a water
circulation able to drive a
cooler water upwelling
along the continental
shore, this in turn
generates the Chla
increase in Jan-Feb and
July-Aug.
This is confirmed by the
SST seasonal behavior
showing a minimum in
these periods.
Page distribution
9
Chla
from SeaWiFS for day 15 Feb. 2002. In occasion of “Red Tides”
High values of Chla are also present near the coasts of the Horn of Africa.
This can be explained taking into account the sea water currents in the
region, but also recalling the phenomenon relating the iron rich dust of
desert origin. This phenomena could be also associated to the occurrence of
proliferation of toxic algae (causing the so-called “red-tide” phenomenon)
results into mass death of fish in the area of interest, as observed and
reported by Kenyan authorities in the last few years.
Therefore, for these characteristics STIOS Team stress that this part of the
ocean is not well documented (in terms of observations) and still conceals in
itself phenomena and features of scientific interest that may be worthwhile
subjects for studies and research.
Page  10
STIOS objectives

Enhancing the knowledge on the seasonal cycle of the pigments
in the Western Indian Ocean
Observations from satellite data will be used to explain and clarify the observed
physical and biochemical seasonal dynamics of the pigments in WIO.
• Scatterometer for providing the surface wind vectors;
• MODIS sensor providing the sea surface temperature (SST) daily;
• OCM-2 sensor for providing information on the biological activities thorough
the ocean colour

Relate the local production with oceanic circulation
To what extent are local/regional variations in production (biomass or Chl-a)
related to variability in oceanic circulation, frontal dynamics and extreme
weather conditions?
Page  11
STIOS objectives

Algae bloom detection
During last few years a red tide phenomenon accompanied by an high fish
death appeared along Kenya coasts and it can be easily detected through
increased Chla content exhibited by SeaWiFS data.
The availability of the OCM data will make possible to formulate an hypothesis
on the reason/precondition of the appearance of this phenomenon very
detrimental for the local economy.
From the study results that West Indian Ocean is a primarily oligotrophic region
with some notable exceptions such as the periods around August and January.
Atmospheric information on the peculiar nature of the aerosols present in the
region are also needed in order to quantify the role of these inputs in fertilizing
the photic zone that is not yet well understood.
Page  12
STIOS objectives

Compare MODIS and OCM chlorophyll data using appropriate
existing algorithms. Comparison with the SeaWiFS historical data
series analysis (1999-2005)
The values of water quality products provided by OCM-2 images will be
compared with those provided by MODIS images, acquired at Broglio Space
Center (BSC) whereas the seasonal variation of the pigment water content will
be compared with the analysis performed previously, based on a time series of
SeaWiFS images acquired at BSC.
Page  13
STIOS objectives

Impact of Ocean Dynamics on the economies of coastal countries
Large ocean currents are important to African economies. Somali Current in the
northeast, are associated with upwelling processes that stimulate high marine
productivity and support considerable fisheries.

Integrating both SST, chlorophyll and wind data to test methods
of production of maps of high potential fishing zones (PFZ).
Analyzing wind data and SST information some peculiar oceanographic features
occurring in the Kenya – Tanzania - Seychelles can be tracked. These features
would be related to the occurrence of seasonal productive areas especially
during the transitional from one monsoon to another (April to May and from
October to November). Since plankton proliferate in moving water masses and
are subject to a maturation process from the initial enrichment zone, tuna
species concentrate along the nearest convergences.
Page  14
time
SeaWiFS and MODIS
data processing
Comparison OCM,
MODIS data
SST, wind, OCM
combined data
analysis
Data validation
results
Page  15
T0 - T0+6
T0+6 - T0+12
T0+12 - T0+18
T0+18 - T0+24
X
X
X
X
X
University of Nairobi,
Department of Physics,
Nairobi,
Kenya
National Environment Management Authority (NEMA)
Popo Road off Mombasa Road
Nairobi,
Kenya
Page  16