Written by Salman Khan (CSIRO) and staff of the AODN
Australia is an island continent surrounded by the Pacific, Indian and Southern Oceans. Wind-waves generated in these ocean basins have a strong socio-economic influence, affecting Australian marine safety and navigation, public beach recreation, the design of our harbours, coastal structures, offshore platforms and shipping, as well as being a potential source of marine renewable energy. It is therefore important to measure and predict ocean wave conditions.
Whilst wave buoys are one way of measuring ocean waves, the coverage around Australia is sparse due to challenges in deploying them in harsh ocean conditions all year round, as well as the high cost of covering Australia’s large marine estate. Satellite radar observations from space can measure global ocean waves repeatedly with high accuracy, and provide a viable source of ocean wave measurements. The spatial coverage provided by satellite remote sensing complements the continuous in-situ buoy records.
Europe’s Copernicus Sentinel-1 A (Jul 2015 onwards) and B (Oct 2016 onwards) Synthetic Aperture Radar (SAR) satellites regularly map Australian waters. Available products from the consequent database includes ocean wave observations from both Sentinel-1 platforms covering their full mission duration, as well as near real-time data (with an approximate 24 hour delay).
The IMOS SAR waves database is built from Sentinel-1 level-2 wave data. The database is optimised to provide a structurally consistent product over time, that is both convenient to use, and compact in size. These benefits will enable users to carry out fast multi-year time-series and event-based analyses not otherwise easily achieved.
Additional quality assurance and control have been applied to the input data to ensure consistency in data structure and types, meta data, and to remove invalid measurements. The database contains full directional ocean swell spectra, swell partitions, and partition bulk parameters of swell significant height and peak period and direction, along with new auxiliary variables. The data are arranged in daily along-track netCDF files that are Climate and Forecast (CF) 1.6 standard compliant, encouraging wider uptake and usage. Currently, the data mainly cover the wider Australian region of interest, with some measurements also extending outside this region, but it is scalable to a global coverage in the future.
The database can be freely accessed via the Australian Ocean Data Network (AODN) Portal. The delayed-mode (up until Nov, 2019) and near real-time data are provided as separate products through the AODN Portal. The database will be regularly updated as new observations become available, as well as improved with better quality control and verification.
Feedback and questions regarding the SAR wave products, or any product available via the AODN Infrastructure, are always welcome please send to info(at)aodn.org.au.