Water Stratification Raster Images for the Gulf of Maine

This geodatabase contains seasonal water stratification raster images for the Gulf of Maine. They were created by interpolating water density (sigma t) values at 0 meters and 50 meters binned by season, and subtracting the water density surface at 0 meters from the water density surface at 50 m. This subtraction (as denoted by the raster value) indicates the differences in water density throughout the Gulf of Maine during the year. The more positive or negative the raster value, the larger the difference between the water density raster at 0 m and the water density raster at 50 m and thus, the more stratified the water. Similarly, the closer the raster value is to 0, the smaller the difference between the water density raster at 0 m and the water density raster at 50 m and thus, the less stratified the water. We tried this density difference calculation with 0 and 10 meters as well as 0 and 30 meters. We chose to use 50 meters as the lower water density depth because water less than 10 meters may have been subject to wind and convective mixing, and water less than 30 meters may have been influenced by internal waves. Water at 50 meters, however, illustrated the greatest difference in stratification strength (buoyancy frequency squared) between layers in the water column (Brown and Irish, 1993). The naming convention of the raster includes the year (or years) included in the the interpolation, the season, and the depth (in meters). So for example, the name: ws_1997_2004_Fall would indicate that this water stratification raster was created by subtracting water density rasters that were interpolated using data from 1997-2004 for the fall. The seasons were defined using the same months as the remote sensing data--namely, fall = September, October, November; winter = December, January, February; Spring = March, April, May and Summer = June, July, August.

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  "https://www.fisheries.noaa.gov/inportserve/waf/noaa/nos/nccos/dmp/pdf/39621.pdf"
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