CMEMS L4 Baltic Sea - Sea Surface Temperature Analysis

This dataset provides near-real-time (NRT) daily multi-sensor gap-free fields (referred to as L4) of foundation Sea Surface Temperature (SST) at a 0.02 x 0.02 degree grid for the Baltic Sea and North Sea. Whereas along swath observation data essentially represent the skin or sub-skin SST, the L4 SST product is defined to represent the foundation (SSTfnd). SSTfnd is defined within GHRSST as the temperature at the base of the diurnal thermocline. It is so named because it represents the foundation temperature on which the diurnal thermocline develops during the day. SSTfnd changes only gradually along with the upper layer of the ocean, and by definition it is independent of skin SST fluctuations due to wind- and radiation-dependent diurnal stratification or skin layer response. SSTfnd corresponds to the temperature of the upper mixed layer which is the part of the ocean represented by the top-most layer of grid cells in most numerical ocean models. It is never observed directly by satellites, but it comes closest to being detected by infrared and microwave radiometers during the night, when the previous day's diurnal stratification can be assumed to have decayed. The processing combines night-time satellite data from infrared radiometers. The data is inter-calibrated and bias corrected before being merged and interpolated using an optimal interpolation scheme to provide daily gap-free fields. The optimal interpolation scheme uses the previous days analysis as a background field. The product is produced in the frame of Copernicus Marine Environment Monitoring Service (CMEMS) and the data available through various tools and protocols with a simple user registration from this service (product identifier: SST_BAL_SST_L4_NRT_OBSERVATIONS_010_007_b).