The project Sea Surface Temperature Diurnal Variability: Regional Extent and Implications in Atmospheric Modeling (SSTDV: R.EX.- IM.A.M.) was initiated within the framework of the European Space Agency's Support to Science Element (ESA STSE). The main focus is twofold: i) to characterize and quantify regional diurnal warming from the experimental MSG/SEVIRI hourly SST fields, for the period 2006-2012. ii) To investigate the impact of the increased SST temporal resolution in the atmospheric model WRF, in terms of modeled 10-m winds and surface heat fluxes. Withing this context, 3 main tasks have been identified. The first task includes the validation and intercomparison of SEVIRI and AATSR data, the construction of the night-time foundation temperature fields and the characterization of the regional diurnal warming. The second task focuses on modeling the diurnal SST variability using the General Ocean Turbulence Model (GOTM). The activities within this task include sensitivity tests on the GOTM set-up, comparison of GOTM, SEVIRI and buoys in point locations and a focus in the North Sea/Baltic Sea with comparisons of GOTM, SEVIRI and 3 diurnal variability schemes. The impact of the diurnal SST variability on atmospheric modeling is the prime goal of the third and final task. This will be examined by increasing the temporal resolution of the SST initial conditions in WRF and by evaluating the WRF included diurnal scheme. Validation of the modeled winds will be performed against 10m ASAR winds and heat flux error estimates will be derived. This study will briefly describe the overall project structure and focus on the first results from WP1. Validation results between the SEVIRI and AATSR Re-processing for Climate (ARC) datasets will be presented. In order to characterize and quantify regional diurnal warming over the SEVIRI disk, a SEVIRI derived reference field representative of the well mixed night-time conditions is required. Different methodologies are tested and the results are validated against SEVIRI pre-dawn SSTs and in situ data from moored and drifting buoys.