|You might think that absolutely
pure water would be perfectly clear and utterly transparent,
but it's actually blue. Water absorbs some of the light that
passes through it. It absorbs red light more than yellow,
yellow more than green, and green more than blue. Only the
deepest blue light can travel very far through water, so a
large mass of water takes on a deep blue color.
What is ocean color?
The "color" of the ocean is
determined by the interactions of incident light with
substances or particles present in the water. The most
significant constituents are free-floating
photosynthetic organisms (phytoplankton ) and
inorganic particulates. Phytoplankton contain
chlorophyll , which absorbs light at blue and red
wavelengths and transmits in the green. Particulate matter can
reflect and absorb light, which reduces the clarity (light
transmission) of the water. Substances dissolved in water can
also affect its color.
What is ocean color data?
The phrase "ocean color data"
refers to accurate measurements of light intensity at visible
wavelengths. As ocean color data is related to the presence of
the constituents described above, it may therefore be used to
calculate the concentrations of material in surface ocean
waters and the level of biological activity. Ocean color
observations made from Earth orbit allow an
oceanographic viewpoint that is impossible from ship or shore
-- a global picture of biological activity in the world's
incident light 入射光线