DAC (Dynamic Atmospheric Correction)

DAC, the dynamic atmospheric correction, removes the sea surface response to atmospheric pressure and wind from altimeter data. Sea level rises about 1 cm for every 1 hPa drop in pressure, the inverted-barometer effect, and at periods shorter than about 20 days the ocean responds dynamically rather than statically. DAC combines a static inverted-barometer term at long periods with a barotropic model, the MOG2D ocean model forced by ECMWF pressure and wind, at high frequency. Applying it before analysis stops storm-driven and high-frequency barotropic signals from aliasing into the mesoscale sea surface height. Copernicus and AVISO distribute the DAC as a standard altimeter correction.