- January 24, 2008
- Posted by: EARSC
- Category: EARSC News
Ocean surface currents have long been the focus of research due to the role they play in weather, climate and transportation of pollutants, yet essential aspects of these currents remain unknown.
By employing a new technique – based on the same principle as police speed-measuring radar guns – to satellite radar data, scientists can now obtain information necessary to understand better the strength and variability of surface current regimes and their relevance for climate change.
Scientists at the SeaSAR 2008 workshop held this week in ESRIN, ESA’s European Centre for Earth Observation in Frascati, Italy, demonstrated how this new method on data from the Advanced Synthetic Aperture Radar (ASAR) instrument aboard ESA’s Envisat, enabled measurements of the speed of the moving ocean surface.
Synthetic Aperture Radar (SAR) instruments, such as ASAR, record microwave radar backscatter in order to identify roughness patterns, which are linked to varying surface winds, waves and currents of the ocean surface. However, interpreting radar images to identify and quantify surface currents had proven very difficult.
Tracking swell waves from space is very important because they are generally preceded by calm water, making it impossible to detect their arrival from shore. Envisat’s Wave Mode acquires small images of the sea surface every 100 km along the satellite orbit. These small images, which depict the wave groups, are then mathematically transformed into wave energy and direction, called ocean-wave spectra.
ESA has provided SAR data to some 500 oceanography projects since 1998 and remains committed to providing continuity to its SAR missions. As part of its Global Monitoring for Environment and Security (GMES) programme, the agency will launch the Sentinels – the first series of operational satellites responding to the Earth Observation needs of GMES, a joint initiative of the European Commission and ESA.
For more information: www.esa.int