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The concentration of chlorophyll A is used as an index of phytoplankton biomass. In the ocean, phytoplankton all contain the chlorophyll pigment, which has a greenish color. Phytoplankton are microscopic organisms that live in watery environments and changes in the amount of phytoplankton indicate the change in productivity of the ocean.
This data archive is used to develop new algorithms and validate satellite data products by matching chlorophyll concentrations measured directly with those estimated remotely from a satellite. These data can also be used to assess atmospheric correction (discussed below) that also can greatly influence chlorophyll concentration calculations.
For instance, algorithms are used to retrieve parameters such as chlorophyll-a(Chl-a) and Suspended Particulate Matter (SPM) concentration, the absorption by colored dissolved organic matter at 440 nm (aCDOM) and secchi depth. [1] The measurement of these values will give an idea about the water quality of the water body being studied.
Typical examples include the Leaf Area Index, biomass, chlorophyll concentration in leaves, plant productivity, fractional vegetation cover, accumulated rainfall, etc. Such relations are often derived by correlating space-derived NDVI values with ground-measured values of these variables.
Chlorophyll-a concentration is a proxy for phytoplankton abundance. Darker shades of green indicate more chlorophyll and more phytoplankton, while shades of blue indicate less chlorophyll and less phytoplankton. [45] The most widely used piece of information from ocean color remote sensing is satellite-derived chlorophyll-a concentration.
[21] [22] [23] In this way, the concentration of chlorophyll within a leaf can be estimated. [24] Methods also exist to separate chlorophyll a and chlorophyll b. In diethyl ether, chlorophyll a has approximate absorbance maxima of 430 nm and 662 nm, while chlorophyll b has approximate maxima of 453 nm and 642 nm. [25]
Chlorophyll a is the most common of the six, present in every plant that performs photosynthesis. Each pigment absorbs light more efficiently in a different part of the electromagnetic spectrum. Chlorophyll a absorbs well in the ranges of 400–450 nm and at 650–700 nm; chlorophyll b at 450–500 nm and at 600–650 nm. Xanthophyll absorbs ...
In situ optical measurements provide a way to: 1) calibrate satellite sensors when they are just beginning to collect data, 2) develop algorithms to derive products or variables like chlorophyll-a concentration, and 3) validate data products derived from satellites.