IMOS - Satellite Remote Sensing - Satellite Altimetry Calibration and Validation Sub-Facility

Satellite-based altimeters provide fundamental observations of sea surface height that continue to underpin our understanding of the ocean’s role in the Earth’s climate system. Understanding changes in mean sea level at global to regional scales is critical for understanding the response of the ocean to a warming climate – both through the thermal expansion of the ocean and the melting of mountain glaciers and polar ice caps. Sea surface height also provides a lens into ocean dynamic processes at regional to local scales. As with all scientific observations, validation of instrumentation is vital to ensure that measurements are accurate and reliable.

The IMOS Satellite Altimeter Calibration and Validation Sub-Facility maintains a suite of instrumentation primarily in Bass Strait, providing the only southern hemisphere in situ calibration and validation site that has operated since the launch of the TOPEX/Poseidon mission in 1992. The facility uses Global Navigation Satellite Systems (GNSS) equipped buoys on the ocean surface as well as an array of sub-surface moored oceanographic instrumentation that includes temperature, pressure and salinity sensors and advanced 5-beam acoustic doppler current profilers (ADCPs). Data from this infrastructure is combined to derive a sustained Sea Surface Height (SSH) record that can be directly compared to altimeter measurements. These data provide important contributions to Ocean Surface Topography Science Team (OSTST) and other mission-specific validation teams including those associated with the Sentinel-6 Michael Freilich, Sentinel-3A and 3B, and SWOT missions. For validation of nadir altimeters, the key metric of interest to mission science teams the altimeter absolute bias, the difference between altimeter and in situ measurements of SSH in an absolute reference frame. Analysis of the absolute bias record over time helps ensure data produced from satellite altimeters are accurate and precise on a global scale.

In addition to the primary site located in Bass Strait, the sub-facility operates some sensors opportunistically at other sites including at the Southern Ocean Flux Station (SOFS) in the Southern Ocean, and at Davies Reef and Yongala in and adjacent to Great Barrier Reef. Data made available from the sub-facility includes:

Bass Strait (various locations corresponding to different altimeter comparison points) 
•   Bottom pressure, temperature and salinity (P, T, S)
•   Water current (U, V)
•   Significant Wave Height (SWH)
•   Sea Surface Height (SSH)
•   Note different temporal extents and sampling rates are provided on a site-by-site basis deploying on deployments and variable of choice.

Southern Ocean
•   Sea Surface Height
•   Significant Wave Height
•   Note two different sampling rates are provided. The temporal extent depends on the SOFS deployment.

Davies Reef and Yongala
•   Bottom pressure, temperature and salinity (P, T, S)
•   Sea Surface Height
•   Note different temporal extents and sampling rates are provided on a site-by-site basis deploying on deployments and variable of choice.

Tags: Countries | Australia, Global / Oceans | Southern Ocean, Marine Features (Australia) | Bass Strait, TAS/VIC, Marine Features (Australia) | Great Barrier Reef, QLD, Marine Features (Australia) | Storm Bay, TAS, Oceans | Bathymetry | Water Depth, Oceans | Ocean Circulation | Ocean Currents, Oceans | Ocean Pressure | Water Pressure, Oceans | Ocean Temperature | Water Temperature, Oceans | Ocean Waves | Significant Wave Height, Oceans | Salinity/density | Conductivity, Oceans | Salinity/density | Salinity, Oceans | Sea Surface Height | Sea Surface Height, Regional Seas | Tasman Sea, States, Territories (Australia) | Queensland, States, Territories (Australia) | Tasmania
Organization: Australian Ocean Data Network