Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Radar altimetry revolutionises the study of the ocean

16.03.2006


Imagine a space tool so revolutionary it can determine the impact of climate change, monitor the melting of glaciers, discover invisible waves, predict the strength of hurricanes, conserve fish stocks and measure river and lake levels worldwide, among other scientific applications. This instrument is not the subject of a science-fiction novel. In fact, four of them are already operating 800 kilometres above Earth.



Fifteen years ago this ground-breaking instrument, called a radar altimeter, was launched into orbit, despite speculation of its usefulness from the wider oceanographic community. Although it took over a decade for its full impact to be realised, its accomplishments have been so great that it is credited with having revolutionised the field of physical oceanography.

In honour of altimetry, oceanographers, glaciologists, hydrologists and geodesists from around the world have gathered in Venice Lido, Italy, at the ‘15 Years of Progress in Radar Altimetry’ symposium, organised by ESA and the French Space Agency (CNES), to celebrate its success. Signifying its vast array of achievements, many have come to honour it for different reasons.


According to one of the pioneers of the altimeter, Massachusetts Institute of Technology’s (MIT) Carl Wunsch, its biggest contribution is conceptual rather than scientific because it changed the way scientists viewed the ocean.

"The greatest achievement of the altimeter is that it has showed us that the ocean system changes rather dramatically everyday and has shifted the view of it from this almost geological phenomenon creeping along very slowly to something much more interesting in which fluid is moving in all directions at all times," Wunsch said.

The radar altimeter offers valuable information on the state of the ocean by providing measurements of the height of the ocean surface. This is done by sending 1800 separate radar pulses down to Earth per second then recording how long their echoes take to bounce back.

Knowing the height of the sea surface tells scientists a great deal about what is happening at lower depths. Before the advent of radar altimetry, oceanographers had no way of looking at the ocean as a whole, which is essential because changes in one part of the ocean will eventually affect the whole rest of the ocean.

Lee-Lueng Fu of NASA’s Jet Propulsion Laboratory came to the symposium to honour the altimeter’s precision: "We are here to celebrate our success because we have managed to measure the height of sea surface with such extreme sensitivity that we are able to detect even two centimetres difference over 100 kilometres."

Because of this extraordinary ability oceanographers are able to measure changes in ocean currents and create a weather chart of ocean circulation for the first time – which Pierre-Yves Le Traon of the French Research Institute for Exploitation of the Sea (IFREMER) states as the instrument’s most outstanding achievement.

Ocean forecasting behaves much the same as weather forecasting: if there is high pressure (signified by higher sea levels), an anticyclonic ocean circulation takes place, which usually translates into good weather conditions, while low pressure (signified by lower sea levels) signifies that a cyclonic ocean current is present.

This type of forecasting has enormous societal and economical consequences. For example, it allows scientists to forecast El Niño events and the flooding of low-lying areas (such as Venice), as well as predict the trajectory of pollutants, which allows oil spills to be contained more quickly by placing barriers in their pathways.

The ability to measure the sea surface height, which varies across the ocean, with such accuracy allowed oceanographers to discover planetary waves, which Paolo Cipollini, of the National Oceanography Centre in the UK, names as the real success story of radar altimetry.

Planetary waves, also called Rossby waves, were theorised to have existed in the ocean as far back as 1930, but it was impossible to know for sure because they occur internally and are very small on the surface, about 10 centimetres high, making them impossible to detect from onboard an oceanographic research vessel.

According to Cipollini, radar altimetry offered proof of these waves for the first time. As oceanographers started mapping the sea surface height, they began seeing the internal waves, which extend 500 or 1000 kilometres underneath the ocean, moving by following the measurements on the surface.

These waves are thought to be very important because they may be responsible for setting the main circulation patterns in the ocean. Cipollini said: “It has been suggested that planetary waves are one mechanism which brings nutrients from the deep sea up to the surface, which would make them important for the carbon cycle.

"So it could be that these mysterious waves that up until 20 years ago we weren’t even able to see are also important for biologists and for people studying how the ocean is reacting to global warming."

ESA has had radar altimeters in orbit since July 1991, when ERS-1 was launched, which was followed by ERS-2 in 1995 and Envisat in 2002. The joint French Space Agency (CNES) and NASA mission TOPEX-Poseidon launched an altimeter in 1992, with follow-up mission Jason-1 flown in 2001.

Mariangela D’Acunto | alfa
Further information:
http://www.esa.int/esaEO/SEMB1RNVGJE_planet_0.html

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Cholesterol-lowering drugs may fight infectious disease

22.08.2017 | Health and Medicine

Meter-sized single-crystal graphene growth becomes possible

22.08.2017 | Materials Sciences

Repairing damaged hearts with self-healing heart cells

22.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>