Example of satellite altimetry verification of model performance. Cryosat observations (filled circles) and tide gauge observations (filled squares) are overlaid the DMI storm surge model field. The surge occurred during the Bodil storm 6-7 December, 2013 and resulted in a 1000 years event in Roskilde, Denmark.
The research and development that will be carried out in this project is focused upon the application of satellite altimetry in shelf sea/coastal sea, the validation of the satellite observations in these regions on operational and climate-related time scales, and the near real time determination of sea level, using a combination of in situ and satellite observations. Two different investigations are proposed to validate the satellite products focusing on shelf- and coastal seas and to extend the use of satellite altimetry observations for operational and climate purposes.
The fields of research are:
- Real time sea level in the North Sea and Baltic Sea from satellite altimetry
DMI has access to a large number of historical and real time tide gauge observations in the North Sea/Baltic Sea and they provide the basis for this study, together with the satellite altimetry observations. Error statistics will be calculated for the Jason-3 and Sentinel 3 SRAL, as part of the Sentinel 3 Cal/Val work, with special focus upon the improvement in the near coastal data retrieval.
A statistical model that combines the altimetry and tide gauge observations has proven to perform similar to the DMI hydrodynamic storm surge model in describing the real time sea level variability in the region. The statistical model has previously been applied within the ESA Esurge project, where an assimilation impact assessment study showed improved performance when the blended satellite-in situ product was assimilated into a hydrodynamic 3-D model (Madsen et al., 2015). It is anticipated that an operational version of the statistical sea level product will be implemented for the real time validation and verification of the model and satellite products.
- Long-term coastal sea level change
DMI has a large interest in climatic coastal sea level variations and trends observed from space, to complement our estimates based on long-term in situ sea level observations. Several altimetry-based products are available, but they are generally using open ocean settings for satellite data retrieval and spatial and temporal averaging. Within the EMODnet project Baltic Checkpoint, over 100 years of 2D sea level variability has been reconstructed, based on in situ observations mainly from PSMSL and 20 years of model reanalysis from the Copernicus Baltic MFC. This reconstruction is independent of satellite data, and we plan to utilize it for validating how close to the coast the altimetry-based climatic sea level products are valid, and where dedicated coastal products would be useful.