Inter-Calibration of Multi-mission Altimeter Systems and Time Series of Dynamic Ocean Topography (iCASiDOT)
The latest GOCE gravity field solutions (e.g. GOCO02S) realize another significant improvement: the actual knowledge of the Earth gravity field allows for the first time to estimate meso-scale pattern of the dynamic ocean topography (DOT) by subtracting the geoid undulations N from sea surface heights h. As geoid undulations and altimetric sea surface heights have completely different spectral content a filter is consistently applied to both, h and N. Compared to GRACE, the latest GOCE gravity field allow to shorten the low pass filter down to a half-width of about 70km, thus approaching meso-scale resolution. In order to avoid any initial gridding of h with undesirable smoothing a method has been developed to estimate the DOT directly along the altimeter profiles. Using the inter-calibrated multi- mission profiles allows to consistently estimate individual DOT profiles for all altimeter systems and subsequently to generate, for example, a gridded time series of 10-day DOT snapshots for a period of actually two decades, 1992 up to the present. This time series realizes the temporal evolution of the dynamic ocean topography and will be translated to geostrophic velocities and eddy kinetic energy complemented by a rigorous error propagation of altimeter error covariances and the full variance-covariance information of the gravity field solution. The project will generate DOT time series on a systematic basis and gradually extend the time series to the full lifetime of Jason-2 and Jason-3 as soon as new consolidated altimeter data becomes available.