NOAA 0.25-degree Daily Optimum Interpolation Sea Surface Temperature (OISST), Version 2.1

This high-resolution sea surface temperature (SST) analysis product was developed using an optimum interpolation (OI) technique. The OISST analysis has a spatial grid resolution of 0.25 degree and temporal resolution of 1 day, spanning from September 1981 to present. The analysis was constructed by combining observations from different platforms on a regular global grid, including Advanced Very High Resolution Radiometer (AVHRR) satellite data, ships, buoys and Argo floats. A spatially complete SST map was produced by interpolating to fill in spatial gaps. The methodology includes bias adjustment of satellite and ship observations (referenced to buoys) to compensate for platform differences and sensor biases. This proved critical during the Mt. Pinatubo eruption in 1991, when the widespread presence of volcanic aerosols resulted in infrared satellite temperatures that were much cooler than actual ocean temperatures, and other degradation of satellite observations. Released in March 2020, Version 2.1 supersedes the previous Version 2. For the January 2016 to present time period, changes include: 1) In-Situ ship and buoy data changed from the NCEP Traditional Alphanumeric Codes (TAC) to the NCEI merged TAC + Binary Universal Form for the Representation (BUFR) data; 2) Addition of Argo float observed SST data; 3) Satellite input changed from METOP-A and NOAA-19 to METOP-A and METOP-B; 4) Revised ship-buoy SST corrections and revised sea-ice-concentration to SST conversion. The data before January 1, 2016 remain the same as Version 2.0. Preliminary product files are produced daily in near real-time (1-day latency) and can be updated in the first few days if critical input data become available after the initial production time. After two weeks, a complete or final product is generated and archived with no additional changes expected. The product is available in netCDF-4 with metadata attributes.