The IMOS Satellite Remote Sensing Facility Sub-Facility Surface Waves (which IMOS formed in 2017) is calibrating, collecting and distributing ocean surface wind and wave data from current and next-generation satellite missions. The sub-facility has just published its first data collection in the AODN Portal, a global database of wind speed and wave height obtained from all the altimeter missions which have flown since 1985.
Satellite altimeters have now been in operation for 33 years, providing global data of wind speed and wave height. The altimeter data is invaluable for many applications, including: design of coastal and offshore structures, the operation of ports and harbours, the routing of ocean-going ships, studies of coastline erosion and investigations of changing climate, to name a few. However, over this 33-year period a total of 13 different satellites have been operational. The data from these satellites is available from a range of different agencies, is in a range of formats and have all been calibrated independently. As a result, it is extremely difficult for users to obtain access to long duration records in a convenient format.
The global database of wind speed and wave height
Integrated Marine Observing System (IMOS) engaged researchers at the University of Melbourne to compile a combined database from all these satellite missions. Importantly, the altimeter observations have all been calibrated against extensive buoy measurements in a consistent manner. As part of this process, any changes in calibration or discontinuities or drift in satellite measurements has also been removed. Finally, every one of the more than 3 billion observations of wind speed and wave height in the database has been assigned a flag indicating the quality of data. The data is for the entire globe from 80S to 80N and is available for 24 hours per day over the 33-year period.
Data use and access
For ease of access, the large database has been split into files each of 1 degree by 1 degree. Users accessing the AODN Portal can specify a region and desired time period and obtain the requested data. At present, the database spans the period 1985 to 2018. The database will be regularly updated as new observations become available.
The main image shows mean monthly global significant wave height during the month of July, as an example of the data use. The example is during the Southern Hemisphere winter when the strong westerly winds in the Southern Ocean generate large waves, as can be seen in the image. These waves propagate into the Indian and South Pacific as swell. Also clear in the image are local influences like the Somali jet which blows along the Horn of Africa at that time of year.
Thank you to Ian Young and Augustinus Ribal of the university of Melbourne for their contribution towards this story.