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|
 Currently
remote sensing by satellite can be used to investigate ocean surface
temperature as well as the amount of chlorophyll a or phytoplankton
concentrations in the ocean.
Phytoplankton are the bedrock of the entire biological productivity
of the ocean. When the ocean experiences eutrophication, or in other
words when it becomes polluted phytoplankton increase reaching abnormal
levels and a red tide is caused. By studying marine concentrations
of chlorophyll a, we can monitor the phytoplankton levels in the ocean
and achieve increased awareness of the pollution levels of ocean. |
 The
most significant merit of using satellite remote sensing is the extremely
broad range of area that can be covered and that the satellite can
sweep this area at once.
Satellites travel in space flying at a rapid speed (7 km/second), so that one
captured image can cover a range of more than 2,000 km
Moreover, these satellites can be used to automatically survey the same region
daily and the highly repetitive nature of this monitoring is another major merit.
It is superior to monitoring from ships in that daily monitoring by ship is incredibly
difficult and monitoring vast areas of the ocean covering hundreds of kilometers
nearly simultaneously is impossible. Given this situation, it is fair to say
that remote sensing data gathered by satellite is eminently suitable as a means
of understanding seasonal and inter-annual changes in a marine environment. |
 As
satellite data is gathered from the sky, this kind of monitoring does
have a few deAdvantages, including the following:
| 1. |
Measurements obtained are less precise than those made on-site. |
| 2. |
In most cases, remote sensing can only gauge the water temperature
of the sea surface. |
| 3. |
Monitoring of visible light and infrared radiation, etc.,
can be made impossible due to cloud cover. |
In addition, satellites sometimes take inaccurate readings of chlorophyll a concentrations,
especially for coastal areas where run-off of muddy water occurs. |
| |
| Monitoring method |
Remote
sensing data |
Sea
tour data |
| Advantages |
| - |
No need to travel to the area monitored. |
| - |
Possible to measure chlorophyll a concentrations
in real time in a planar way. |
| - |
Data is often available for free when it is required
for research purposes. |
|
| - |
Actual numerical measurements can be taken. |
| - |
Acquiring data in a vertical direction is possible. |
|
| Disadvantages |
| - |
Mud, silt and non-phytoplankton material can make
estimations of chlorophyll a levels difficult. |
|
| - |
Travel to the site to be monitored as well as manpower
and a vessel are required. |
| - |
Special analytical technology is required to obtain
chlorophyll a data. |
| - |
This data is limited to one point. |
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Ministry of the Environment , Northwest Pacific Region Environmental Cooperation Center
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