Combining Satellite Altimetry, Tide Gauge Observations and an Oceanographic Model to Derive the Baltic Sea Mean Sea Surface Topography
Kristin Novotny(1) , Andreas Lehmann(2) , and Reinhard Dietrich(1)
Technische Universität Dresden,
(2) Leibniz-Institut für Meereswissenschaften, Düsternbrooker Weg 20, 24105 Kiel, Germany
In the Baltic Sea, the sea-level variability is dominated by meteorologically forced fluctuations with large seasonal and interannual variations. Besides the observations of satellite altimeters, a dense network of tide gauge measurements is available to determine these sea-level variations. Moreover, a high-resolution oceanographic model of the Baltic Sea provides sea-level heights that largely reflect the high-frequency sea-surface variations.
The different information can be combined in such a way that the variance of the altimetric sea-level heights can be substantially reduced. To achieve this reduction, the long-term variations as obtained from tide gauges and the short-term variations provided by the oceanographic model are applied to the altimeter data. The resulting smoothed altimeter time series form the basis for the estimation of mean sea-surface heights. The application of a geoid model then yields the mean sea-surface topography (MSSTop).
A high spatial resolution of the resulting MSSTop is achieved by the combination of several altimetric missions. For this purpose, observations of Jason-1, ERS-2, and Envisat are tied to the observations of TOPEX by minimizing the crossover point differences. This also provides information about the relative biases between the different altimeter missions.
The presentation will focus on how the sea-surface heights from the different sources and techniques can be combined, and the error budget of the resulting MSSTop will be discussed.