The Coral Reef Temperature Anomaly Database (CoRTAD) Version 5 - Global, 4 km Sea Surface Temperature and Related Thermal Stress Metrics for 1982-2012 (NCEI Accession 0126774)

[Text below adapted from: Selig, E.R., K.S. Casey, and J.F. Bruno (2010). New insights into global patterns of ocean temperature anomalies: implications for coral reef health and management, Global Ecology and Biogeography, https://doi.org/10.1111/j.1466-8238.2009.00522.x. Hereafter referred to as "SCB2010".]

The CoRTAD was developed using 1982-2012 data from the Pathfinder Version 5.2 collection (Casey et al., 2011) produced by the National Oceanic and Atmospheric Administration's (NOAA) National Oceanographic Data Center (NODC) and the University of Miami's Rosenstiel School of Marine and Atmospheric Science. These sea surface temperature data are derived from the Advanced Very High Resolution Radiometer (AVHRR) sensor and are processed to a resolution of approximately 4.6 km at the equator. These data have the highest resolution covering the longest time period of any satellite-based ocean temperature dataset. Daytime and nighttime data were averaged weekly using data with a quality flag of 4 or better. This level is a commonly accepted cutoff for "good" data (Kilpatrick et al., 2001, Casey and Cornillon, 1999). Previous versions of CoRTAD (versions 1-3) also incorporated pixels up to 5 degrees warmer than a course resolution reference SST based on the Reynolds Optimum Interpolation Sea Surface Temperature (Weekly, 1-degree OISST version 2.0). Since Pathfinder Version 5.2 already uses a finer resolution reference field (25 km Daily OISST) this additional step was not incorporated here in CoRTAD Version 5, or in the previous CoRTAD Version 4 (Casey et al., 2012). These processes resulted in a weekly SST dataset that is roughly 80% gap free. To create a gap-free dataset for analysis, 3 x 3 pixel median spatial fill was used. A temporal fill was then performed using the nonlinear least squares data fitting (Levenberg-Marquardt algorithm) in SLATEC Common Mathematical Library (in public domain) to fill the remaining gaps. This conservative approach was chosen because it provided interpolated SSTs that are bounded by the nearest available values in time. It also used data from only a very limited spatial domain, which is an important consideration given the variability of coral reef environments. Using these gap-filled data, we then created site-specific climatologies for each reef grid cell to describe long-term temperature patterns over the 31-year dataset. The climatology was generated using a harmonic analysis procedure that fits annual and semi-annual signals to the time series of weekly SSTs at each grid cell: climSST(t) = A*cos(2pi*t + B) + C*cos(4pi*t + D) + E (1) where t is time, A and B are coefficients representing the annual amplitude and phase, C and D are the semi-annual amplitude and phase, and E is the long-term temperature mean. Others have used similar approaches for generating climatologies because they are more robust than simple averaging techniques, which can be more susceptible to data gaps from periods of cloudiness (Podesta et al., 1991, Mesias et al., 2007). Please note in both CoRTAD Versions 4 and 5, a gap exists in the Pathfinder 5.2 dataset from 1994 day 275 to 1995 day 17 since Level 1B GAC data from NOAA-9 is not available from the NOAA archives. For these 3.5 months SST has been interpolated from Pathfinder 5.0 and 0.17K is subtracted to transform the data to the skin temperature basis of Pathfinder Version 5.2. In CoRTAD Version 5, the data are not stored in separate geographic tiles like in Version 4 and earlier. Instead, each data file contains the entire global coverage for a related grouping of CoRTAD parameters.

Following are the version changes at glance:
Version 5, 1982-01-02 - 2012-12-28, Global 4320x8640x1617 netCDF-4.1.2
Version 4, 1981-10-31 - 2010-12-31, Global 4320x8640, Tile 540x540, netCDF-4 Classic
Version 3, 1982-01-01 - 2009-12-31, Global 4096x8192, Tile 512x512, HDF5
Version 2, 1982-01-01 - 2008-12-31, Global 4096x8192, Tile 512x512, HDF5
Version 1, 1985-01-01 - 2005-12-31, Global 4096x8192, Tile 512x512, HDF4
NCEI Accession Numbers: v5 0126774; v4 0087989; v3 0068999; v2 0054501; v1 0044419