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The Near-Surface Sea Temperature (NSST) foundation temperature analysis is posted daily at 12Z at 1/12 degree resolution. It is part of the Global Forecast System (GFS) products. The foundation temperature, the temperature at the base of the oceanic diurnal warming layer, is analyzed at a 6-hourly temporal resolution together with other atmospheric variables. Analysis is performed by GSI (Global Statistical Interpolation), the atmospheric data assimilation system in the GFS.
The NSST foundation temperature, plus NSST diurnal warming model and skin-layer cooling parameterization, provides the required thermal lower boundary conditions, usually called SST (Sea Surface Temperature), for the GFS atmospheric model and transfer radiative model (CRTM). Unique to the NSST, satellite radiances, rather than SST retrievals as in other SST products, are assimilated.
The NSST became operational in the GFS in July 2017 and is continuously improved with upgrades to the GFS.