(Version 1.0, released on 12 February 2018)
NOAA Coral Reef Watch (CRW) produces a number of daily global 5km (approximately 0.05 degree) sea surface temperature (SST) based anomaly products. All of these rely on having an accurate climatology and a long enough time series of SST data that has consistent bias and errors and is either part of a near-real-time SST product or related to one.
Herein we present CoralTemp. Developed from two, related reanalysis (reprocessed) SST products and a near-real-time SST product, CoralTemp is one of the best and most internally consistent daily global 5km SST products, spanning January 1, 1985 to the present.
The source data for CoralTemp are from a combination of:
1) NOAA/National Environmental Satellite, Data, and Information Service's (NESDIS') operational near-real-time daily global 5km Geostationary-Polar-orbiting (Geo-Polar) Blended Night-only SST Analysis (the source data for which are shown in Figures 1 and 2);
2) NOAA/NESDIS' 2002-2016 reprocessed daily global 5km Geo-Polar Blended Night-only SST Analysis (the source data for which are shown in Figures 1 and 2); and the
3) 1985-2002 daily global 5km SST reanalysis produced by the United Kingdom Met Office, on the Operational SST and Sea Ice Analysis (OSTIA) system (the source data for which are displayed in Figure 3).
Figure 1: Timeline of availability of polar-orbiting satellite datasets used in NOAA's daily global 5km Geo-Polar Blended Night-only SST Analyses (both the near-real-time and reprocessed products).
Figure 2: Timeline of availability of geostationary satellite datasets used in NOAA's daily global 5km Geo-Polar Blended Night-only SST Analyses (both the near-real-time and reprocessed products).
NOAA's daily global 5km Geostationary-Polar Blended Night-only SST Analyses (both the near-real-time and reprocessed products) utilize sensors from multiple geostationary and polar-orbiting satellites to derive a global SST data field at a resolution of 5km (approximately 0.05 degree). The few remaining gaps are filled using optimal interpolation through space and time (Maturi et al. 2017). Bias corrections originally used the NOAA National Centers for Environmental Prediction (NCEP) real-time global SST. However, in 2016, the NOAA 5km Geo-Polar Blended SST product (which CRW's 5km satellite monitoring for coral reefs is based on) switched to using OSTIA as the bias correction.
In addition, NOAA reprocessed the 5km Geo-Polar Blended SST back to 2002, thereby providing good overlap with the OSTIA reanalysis dataset, negating the need to use the near-real-time OSTIA product to bridge the gap between NOAA's near-real-time 5km Geo-Polar Blended SST product and the OSTIA reanalysis. The OSTIA reanalysis and NOAA's reprocessed 5km Geo-Polar Blended SST dataset were linearly merged over a period of 29 days, from November 1-29, 2002. Since this is a full tidal cycle, by gradually merging the two datasets over this period, any local differences between the two datasets were minimized. The merge point between NOAA's reprocessed and near-real-time 5km Geo-Polar Blended SST datasets was performed over a 29 day period, from October 1-29, 2016.
CoralTemp SST data are presented in degrees Celsius, with a land mask of -32,768 embedded within the data. An additional array is included in the data files that provides sea ice concentration values, so those users who wish to process SST in the ice prone high latitudes have the ability to choose an appropriate sea ice mask for their purpose(s). The NOAA 5km Geo-Polar Blended SST products derive their sea ice concentrations from the NCEP sea ice analysis (Maturi et al. 2017), whereas the OSTIA products derive their sea ice concentrations from the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Ocean and Sea Ice Satellite Application Facility (OSI SAF) sea ice concentration dataset. The OSTIA reanalysis and NOAA's reprocessed 5km Geo-Polar Blended SST dataset do not differ for the period of overlap.
These efforts provide consistency between the NOAA 5km Geo-Polar Blended SST Analyses (both the near-real-time and reprocessed products), the OSTIA reanalysis, and CRW's 5km satellite products for coral reefs, allowing for the creation of CoralTemp.
Maturi, E.; Harris, A.; Mittaz, J.; Sapper, J.; Wick, G.; Zhu, X.; Dash, P.; Koner, P. A New High-Resolution Sea Surface Temperature Blended Analysis. Am. Met. Soc., 2017, 1015-1026.
Roberts-Jones, J.; Fiedler, E.K.; Martin, M.J. Daily, Global, High-Resolution SST and Sea Ice Reanalysis for 1985-2007 Using the OSTIA System. J. of Climate, 2012, 25, 6215 – 6232.