This study presents some preliminary results of the ESA Support To Science Element (STSE) funded project on the Diurnal Variability of the Sea Surface Temperature, regarding its Regional Extend and Implications in Atmospheric Modelling (SSTDV:R.EX.–IM.A.M.). Comparisons of SEVIRI SST with AATSR show zero biases and standard deviations around 0.5 K mostly in the Tropics where SEVIRI is found colder. Sensitivity tests on the methodology to derive foundation temperature fields show that using only quality 5 SEVIRI data results in warmer foundation fields while there is an added 0.2 K variability when using multi-day composites. Diurnal warming signals exceeding 2 K are identified in the European Seas but also in the mid-latitudes of the North and South Atlantic as well as in areas with strong currents. In the attempt to connect temperature measurements from satellites and in situ instruments, the 1-dimensional General Ocean Turbulence Model (GOTM) is applied. Preliminary results show that the initial temperature and salinity profiles may give a warmer start-up in the model while the light extinction scheme is a controlling factor for the amplitude and vertical extend of the daily signal.