The North Atlantic Climate System Integrated Study (ACSIS) Atlantic Ocean medium resolution SST dataset is a 5-day field of Sea Surface Temperature (SST) on a ½ degree by ½ degree grid from 1950 to 2014 and covers the Atlantic Ocean.

The dataset is based on in situ ship and buoy SST observations from the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) Revision 3. Measurements which fail initial quality control checks are rejected and for each grid box where there is data a trimmed mean and sample standard deviation are calculated to produce super-observations. These are then expressed as anomalies from the 1981-2014 Climatology (mean, annual, semi-annual and tri-annual) from the European Space Agency (ESA) Climate Change Initiative (CCI) SST dataset (version 2.0) derived from satellite observations. The measurements are then interpolated using Kriging to infill gaps and estimate uncertainties. The spatial covariance used in the Kriging was derived from the CCI SST analysis residuals (CCI SST analysis minus the CCI SST climatology). After interpolation, bias corrections derived from the HadSST.4.0.0.0 dataset are applied.

The dataset is available as annual CF complaint NetCDF files, with a total of 65 annual files available. Each file contains: the 5 day mean sea surface temperature; the corresponding climatological value, the sea surface temperature anomaly and the uncertainty in the sea surface temperature.

The new dataset has been developed as part of the UK North Atlantic Climate System Integrated Study (ACSIS) for use in validation and comparison with regional climate models. Other potential uses include boundary forcing for regional reanalyses, monitoring and assessment of regional climate change and other studies requiring SST at a resolution higher than typical for the in situ products (i.e. < 1 month, < 1°) and spanning the satellite and pre-satellite era.