Practical Applications Of Nimbus-7 Coastal Zone Color Scanner Data

The Coastal Zone Color Scanner (CZCS) was launched on Nimbus-7 in October of 1978 as a research tool to determine if the biological and non-biological content of the ocean could be determined by remote sensing to a degree of accuracy useful for oceanographers. By the end of the first year of the sensor's life, the algorithms for calculating such things as pigment concentration and diffuse attenuation coefficient had been well developed, and ship measurements showed that the agreement with surface truth was better than the original goal set for the sensor data product in the open ocean. Near shore, where high sediment levels prevented the atmospheric correction algorithm from working properly, gradients could be observed, but quantitative accuracy was not as good as in offshore in waters ranging from pigment concentrations from near 0 to 2 milligrams per cubic meter. Since the sensor and spacecraft designed to last for one year have now operated for over five years, schemes have been devised to use the data in a practical manner for both monitoring long term effects such as pigment concentration throughout the year along the East Coast, and direct assistance to fishermen in the Gulf of Mexico and on the West Coast. The pigment concentration derived from the CZCS imagery has been shown to agree very well with the maps produced by ships at sea, and to cover a much larger area than the ships could possibly cover in a very short period of time. This added capability allows the ships to be utilized on more specific tasks rather than simply making grid measurements over large areas such as the Chesapeake to Cape Cod, and requiring one month of ship time to produce an image. The West Coast Fisheries Demonstration Project utilizing the CZCS uses real time imagery, collected at the Scripps Institution, processed overnight, and transmitted to tuna fishermen the next day from Monterey, California. Comparison of tuna catch with the color data has shown that the tuna are not sensitive to temperature as originally thought, but are, in fact, hunting by staying in the clear water on the edges of the cool more turbid water where their prey normally live. Since the tuna hunt by eye, they must stay in the clear water in order to be able to see the other fish that they prey upon. Comparison of fish catch with the imagery shows that the largest fish catch per day is quite clearly correlated with this water mass boundary between the clear and the turbid water. In the Gulf of Mexico, a serious hypoxic condition was monitored using the CZCS data. A large body of hypoxic water preventing the migration of shrimp from the shore out into the Gulf was clearly defined using the satellite data, and the magnitude of the problem could be quickly analyzed by personnel of the National Marine Fisheries Service in Bay St. Louis, Mississippi. These applications, far from the original intent of the instrument, are ongoing, however, the wisdom of starting new projects is debatable since the CZCS has now exceeded its original expected lifetime by a factor of five, and the United States has no plan to fly a replacement instrument.