The waves that thrashed the southern port of Saint Pierre, leaving two fishermen missing, causing several piers to collapse and flooding several homes and businesses, originated south of Cape Town, South Africa, and travelled northeast for nearly 4000 km over a period of three days before slamming into Reunion Island.
Dr Bertrand Chapron of IFREMER, the French Research Institute for Exploitation of the Sea, and Dr Fabrice Collard of France's BOOST Technologies in Brest located and tracked the swells using standard processed Synthetic Aperture Radar (SAR) ESA products.
"Swells are still surprise factors, which can unfortunately be deadly," Chapron said. "The SAR Wave Mode product allows us to locate and systematically track swells globally. In the near future we anticipate using SAR wave data to predict their arrival time and intensity."
Although waves were forecast to hit Reunion Island, their intensity was predicted to be only a couple of metres, Collard explained.
"Because strong swells are preceded by calm water, it is impossible to detect their arrival from shore," Collard said. "SAR is the swell instrument and can typically observe swell periods in the range of 12 to 25 seconds."
A larger wave period correlates to a more extreme wind event. The one that hit Saint Pierre, Reunion Island, had a 19-second range and initially originated from very intense storm winds on 8 May.
Approaching the coastline, the wave system slows down and individual waves increase to reach at least two times the mean average of their initial wave height easily. For instance, a 5-metre significant wave height system can hit the coast with the height of 10 metres.
Chapron and Collard are working on a project that will make data for global swells available to scientists and users by the end of the year as a demonstration. The products will be useful for weather centres to complement the accuracy of their sea forecast models.
Envisat is equipped with an advanced version of the SAR instrument, Advanced Synthetic Aperture Radar (ASAR), flown on the ERS-1 and ERS-2 missions. Its wave mode acquires 10 by 5 km small images, or 'imagettes', of the sea surface every 100 km along the satellite orbit. These small ‘imagettes’, which depict the individual wave heights, are then mathematically transformed into averaged-out breakdowns of wave energy and direction, called ocean-wave spectra, which ESA makes available to scientists and weather centres.
A typical SAR satellite images a swath of 400 km, enough to capture complete 'mesoscale' phenomena such as tropical storms. While optical satellite images show the swirling cloud-tops of a hurricane, a SAR image pierces through the clouds to show the sea surface roughness and its modulation through the combination of wind wave and currents.
Waves of all wavelengths and travelling in several directions are generated by storms. Upon leaving the storm, they disperse and those with the longest wavelengths travel the fastest. During the Envisat Symposium held in Montreux, Switzerland, from 23 to 27 April 2007, Chapron and Collard presented for the first time a demonstration of swell tracking across the Pacific Ocean over a period of 12 days using Envisat ASAR Wave mode.
The same swell tracking was applied for the identification of the waves that hit Reunion Island last weekend. Independent satellite wind observations confirmed the position of the storm as the origin of the huge waves.
As part of the Global Monitoring for Environment and Security (GMES), a joint initiative of the European Commission and ESA, the space agency has undertaken the development of Sentinel-1, a European polar-orbiting satellite system for the continuation of SAR operational applications. The Sentinel-1 SAR instrument will have a dedicated wave mode allowing the Near Real Time tracking and forecasting of swell for European users.
Mariangela D'Acunto | alfa
Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie
Modeling magma to find copper
13.01.2017 | Université de Genève
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction