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Diffuse Attenuation Coefficient at 490nm Wavelength (K490)
Program: NASA Earth Observing System
Sensor: Moderate Resolution Imaging Spectroradiometer (MODIS)
Data Stream: Recorder LAC
Primary Geophysical Parameter: Diffuse Attenuation Coefficient
Nominal Accuracy: unknown
Spatial grid: 0.05 degrees longitude by 0.05 degrees latitude, geographic
Spatial coverage: Global, 180W to 180E Longitude, 75S to 75N Latitude
Temporal Coverage: 2006 - ongoing
CoastWatch provides science quality diffuse attenuation coefficient data at 490nm wavelength from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua and Terra satellites. These data are received and processed by NASA's Goddard Space Flight Center (GSFC). The diffuse attenuation coefficient is a good measure of water clarity. This is a Science Quality dataset, which is made available on a delayed time frame to allow for improvements in the data processing.
CoastWatch offers diffuse attenuation coefficient data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA's Aqua satellite. Information on the Aqua and Terra satellites, the MODIS sensor, and NASA's Ocean Color projects can be found on NASA's OceanColor Web. The GSFC receives and processes raw satellite data using the SeaWiFS Data Analysis System (SeaDAS) software (Fu et al., 1998). Satellite data is processed to diffuse attenuation coefficient using an updated version of Mueller, 2000. For more information on the NASA product, see http://oceancolor.gsfc.nasa.gov/PRODUCTS/k490.html .
Data is made available at 5.5km resolution for the Pacific Ocean Basin. The data are mapped to an equal angle grid of 0.05 degrees latitude by 0.05 degrees longitude using simple arithmetic means to produce single-pass and composite images of various duration (1,3,8, and 14-days, and monthly).
Despite our best efforts, incorrect data may often appear within near real time data sets. NOAA CoastWatch accepts no liability for use of these data products. It is recommended that these products NOT be used for navigation.
If this data is used for presentation or publication, please acknowledge the NOAA CoastWatch Program, NASA Goddard Space Flight Center, OceanColor Web.
Fu, G., Baith, K. S., and McClain, C. R. "SeaDAS: The SeaWiFS Data Analysis System", Proceedings of "The 4th Pacific Ocean Remote Sensing Conference", Qingdao, China, July 28-31, 1998. 73-79.
Mueller, J.L. 2000: SeaWiFS algorithm for the diffuse attenuation coefficient, K(490), using water-leaving radiances at 490 and 555 nm. In O'Reilly, J.E. and co-authors: SeaWiFS Postlaunch Calibration and Validation Analyses, Part 3. S.B. Hooker and E.R. Firestone, Eds., NASA/TM-2000-206892, Vol. 11, NASA Goddard Space Flight Center, Greenbelt, Maryland, 24-27.