Dynamic Atmosphere Correction

Dynamic Atmosphere Correction

The sea surface is pushed downward by atmospheric pressure, so as atmospheric pressure changes, the amount by which the sea surface is pushed downward also changes, creating both spatial and temporal variations in sea surface height that are due to the atmosphere, rather than the sea itself. The dynamic atmosphere correction (DAC) allows correction of high frequency variability induced by pressure and wind-induced forcing of the ocean surface, through a model that includes the properties of the ocean itself (e.g., depth variations and water momentum). In the case of S6-MF this model is the MOG-2D model (Carrère and Lyard, 2003). This provides three levels of data quality: one for real-time processing, based on forecast pressure variations, one based on the preliminary MOG-2D file, and one on the corrected (precise) file. Comparisons have shown similar performance between the latter of these files and using ERA data. All MOG-2D data are provided on a 6-hourly basis and interpolated for intermediate times, using a 400 km grid over deep ocean areas and a 20 km grid in coastal regions. Spatial interpolation is performed using a bilinear interpolation method.

Uncertainties associated with the dynamic atmosphere correction were not considered during the first phase of this project.