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Ocean Surface Topography from Space
Australian Altimetry: From Precision Sea Level to Near-Real Time Delivery and Applications


Christopher Watson - (University of Tasmania, Discipline of Geography and Spatial Sciences)

  Dr Benoit Legresy
Dr Madeleine Cahill
Dr David Griffin
Dr Mark Hemer
Dr Peter Oke

The Bass Strait validation site
The Bass Strait validation site with historical comparison point on the TOPEX/Jason series ground track (red line) and Sentinel-3A and 3B comparison points on respective crossovers (magenta and blue lines respectively).
This proposal continues the long association of Australian scientists at the University of Tasmania and CSIRO with the OSTST, supported in part by the Australian Integrated Marine Observing System (IMOS). The assembled team will contribute work on four diverse thematic areas of investigation: in situ calibration and validation, global and regional sea level change, near real time applications, and coastal altimetry (with a special focus on current SAR and future InSAR missions).  
The cal/val work will see the continuation of the Bass Strait validation site which has contributed estimates of absolute altimeter bias since the launch of the TOPEX/Poseidon mission in 1992. Over the study period the Bass Strait site will be further enhanced to facilitate a regional multi-mission satellite altimetry calibration/validation system that will span NASA/CNES and ESA (with respective partner agencies) altimeter missions.
We plan to continue our long association with studies related to sea level rise and variability, with a focus on the ongoing improvement and interpretation of the sea level climate data record over the satellite period. We seek to investigate changes to the contributors to the sea level budget, with the aim of quantifying and understanding what is likely to be accelerating sea level over the altimeter period. Comparisons with the global tide gauge network used in conjunction with estimates of vertical land motion will be used to assess error characteristics within each dataset. Regionally, we will further assess sea level change and variability in the Australian region and its connection to surrounding oceans.
Bathymetry (colours) and surface current velocity (vectors) over the Bass Strait domain
Bathymetry (colours) and surface current velocity (vectors) over the Bass Strait domain
Work on near real time applications will include continuation of the Australian real-time multi-mission gridded sea level analysis (SLA) system which incorporates visualization with other satellite (SST, Chlorophyll) and in-situ data delivered via the IMOS OceanCurrent website ( The gridded SLA and geostrophic velocities have varied purposes, from a first check of altimeter data input into Australia’s data-assimilating global ocean models (OceanMaps and BRAN) to informing Australia’s search and rescue agency.  
The final component involves further exploiting altimeter data in the coastal domain with a special focus on current SAR and future InSAR missions. Here the Bass Strait study region will again be a focus with the further development of a high resolution ocean model that is embedded within the large scale operational model over the domain. In situ and modelled data will aid interpretation of the altimeter data and contribute to the validation of next generation InSAR missions.

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