The University of Rhode Island's Graduate School of Oceanography (GSO), with funding from NASA, has navigated and processed 5-channel AVHRR passes obtained from receiving stations for regions of the Northwest Atlantic, Northwest Pacific, and Northeast Pacific during the period of 1985-2001. These data have been processed at full 1.1 km resolution, the highest possible for a regional AVHRR data set. The archive is served via our OPeNDAP server at URI-GSO and the data can also be accessed by downloading the respective GUI (Graphical User Interface) from the Matlab OPeNDAP Ocean Toolbox.

This archive consists of sea surface temperature (SST) fields derived from Advanced Very High Resolution Radiometer/2 (AVHRR) data obtained from the NOAA Tiros-N series of polar-orbiting satellites, starting with NOAA-9 in 1985 and ending with NOAA-14 in 2001. Collaboration with local receiving stations enabled URI to obtain and process (at full resolution) all daily AVHRR passes during the periods of 1985-2001 for the Northwest Atlantic, 1985-1999 for the Northwest Pacific and 1992-1999 for the Northeast Pacific. For example, the images in the Northwest Atlantic archive average about 1000 per year and were processed using raw satellite data downlinked by the Wallops Island receiving station and transmitted to URI from the University of Miami Rosentiel School for Marine and Atmospheric Studies (RSMAS). Similar collaborative efforts were made by the University of Washington in Seattle and the University of Tokyo.

The processing stream begins with the ingestion step, when the raw AVHRR digital counts are converted to calibrated radiance values. During ingestion, the geo-referencing information is also obtained and applied to the data, determining the location of the satellite along the orbital track. For more accuracy, each satellite pass is then manually navigated. Once the ingestion and navigation are complete, the Pathfinder SST algorithm, developed at the University of Miami, is applied to the navigated passes in order to calculate Pathfinder sea surface temperature values. This atmospheric correction algorithm is a statistical algorithm that relies on coefficients derived from a "matchup" database, a set of coincident in situ and satellite SST measurements. Full descriptions of the Pathfinder SST algorithm and of the steps in Pathfinder processing are available for those interested. Each satellite pass is then remapped to a common coordinate system so that each image in the archive covers the same area. The URI cloud screening program was applied to the data which effectively masked cloud covered pixels in the final SST fields presented in the archive.



Carl Wolfteich
University of Rhode Island - GSO