Remote Sensing of Upwelling - Total Actual Radiation

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While this region would seem to be optimal for a satellite sensor to detect chlorophyll a, phytoplankton also contain other often taxonomic-specific photoactive pigments such as chlorophyll b, phycoerythrin, fucoxanthin, and peridinen. These accessory pigments absorb light at additional wavelengths, complicating the electromagnetic signal that is radiated from phytoplankton cells. Other factors such as water turbidity and the presence of dissolved organic material will also absorb and scatter light, as will the atmosphere the light passes through, further confusing the electromagnetic signal that is actually received by satellites.

For this reason, in practice satellites must sample the level of energy that is received across several key wavelengths and then use empirically-established algorithms that quantify the various relationships to determine the actual chlorophyll levels that are present. By examining the pattern of light intensity that reaches the satellite sensor over these wavelengths (that is, the proportion of light that is being reflected vs. absorbed across the electromagnetic spectrum), the individual factors responsible for the pattern can be teased apart - an important one of which is chlorophyll a.

satellite detection of phytoplankton bloom

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