Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Global air pollution map produced by Envisat’s SCIAMACHY

12.10.2004


Based on 18 months of Envisat observations, this high-resolution global atmospheric map of nitrogen dioxide pollution makes clear just how human activities impact air quality.



ESA’s ten-instrument Envisat, the world’s largest satellite for environmental monitoring, was launched in February 2002. Its onboard Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) instrument records the spectrum of sunlight shining through the atmosphere. These results are then finely sifted to find spectral absorption ’fingerprints’ of trace gases in the air. Nitrogen dioxide (NO2) is a mainly man-made gas, excess exposure to which causes lung damage and respiratory problems. It also plays an important role in atmospheric chemistry, because it leads to the production of ozone in the troposphere – which is the lowest part of the atmosphere, extending up to between eight and 16 kilometres high.

Nitrogen dioxide is produced by emissions from power plants, heavy industry and road transport, along with biomass burning. Lightning in the air also creates nitrogen oxides naturally, as does microbial activity in the soil.
Localised in-situ measurements of atmospheric nitrogen dioxide are carried out in many western industrial countries, but ground-based data sources are generally thin on the ground.



Space-based sensors are the only way to carry out effective global monitoring: the first satellite sensitivity to tropospheric nitrogen dioxide was demonstrated with the Global Ozone Monitoring Experiment (GOME) on ESA’s ERS-2. However GOME was only a sub-scale precursor of the German, Dutch and Belgian financed SCIAMACHY flying on Envisat.

While both instruments function in the same way, GOME has a limited spatial resolution of only 320 x 40 km, compared to a typical 60 x 30 km with SCIAMACHY, which also observes the atmosphere in two different views –downwards or ’nadir’ looking as well as making ’limb’ observations in the direction of flight – and has a significantly larger spectral range than its predecessor.

Teams from the Universities of Bremen and Heidelberg in Germany, the Belgian Institute for Space Aeronomy (BIRA-IASB) and the Royal Netherlands Meteorological Institute (KNMI) have successfully processed SCIAMACHY data to generate the sharpest maps yet made of the vertical columns of tropospheric nitrogen dioxide. "The higher spatial resolution delivered by SCIAMACHY means we see a lot of detail in these global images, even resolving individual city sources" said Steffen Beirle of the University of Heidelberg’s Institute for Environmental Physics, responsible for the map shown above.

"High vertical column distributions of nitrogen dioxide are associated with major cities across North America and Europe, along with other sites such as Mexico City in Central America and South African coal-fired power plants located close together in the eastern Highveld plateau of that country. "Then a very high concentration is found above north eastern China. Also across South East Asia and much of Africa can be seen nitrogen dioxide produced by biomass burning. Ship tracks are visible in some locations: look at the Red Sea and the Indian Ocean between the southern tip of India and Indonesia. The smoke stacks of ships crossing these routes send a large amount of NO2 into the troposphere.

This map is average out across all available data, spanning 18 months. This has the effects of reducing seasonal variations in biomass burning and also those due to human activity changes due to the time of year." Like GOME, SCIAMACHY works by observing atmosphere-scattered ultraviolet, visible and near-infrared radiation. The hard work comes on the ground, where researchers attempt to retrieve very weak trace gas absorption patterns within the overall spectrum of backscattered light, a feat comparable to finding a needle in a haystack.

The method they use is called Differential Optical Absorption Spectroscopy (DOAS), which is basically a complex filtering process also used with ground-based air-sampling instruments. DOAS removes the predominant spectral ’noise’ from air particles’ Rayleigh scattering of light (the same phenomenon that causes the sky appear blue) along with the absorption patterns from the oxygen, nitrogen and water molecules that make up most of the atmosphere.

Left behind after these subtractions is the desired ’signal’ of narrower trace gas spectral absorption patterns, to be identified against sample cross sections. Applied to SCIAMACHY results, this technique is sufficiently sensitive to retrieve columns lower than a few parts of nitrogen dioxide per billion parts of air. To give an idea of scale, above highly polluted conurbations such as London, NO2 mixing ratios can reach values as high as a hundred parts per billion.

Nitrogen dioxide maps like that shown here have been produced using nadir-sounding data: while NO2 vary widely across the troposphere they are evenly spread across the upper atmosphere, the stratosphere. So nitrogen dioxide levels measured above the remotest parts of the Pacific were used to determine a general column for stratospheric nitrogen dioxide, which could be subtracted from the global data to determine tropospheric vertical column values.

"Results from this and other similar sensors could be used for chemical weather and air quality prediction in future," Beirle added. "For now we are focused on using the SCIAMACHY results to quantify the contributions of the different sources of nitrogen oxides – such as fossil fuel combustion, biomass burning, lightning – especially as the value of the latter is still highly uncertain."

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

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling 'fast fashion' to reduce waste and pollution
03.04.2017 | American Chemical Society

nachricht Litter is present throughout the world’s oceans: 1,220 species affected
27.03.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

How Plants Form Their Sugar Transport Routes

28.04.2017 | Life Sciences

Protein 'spy' gains new abilities

28.04.2017 | Life Sciences

Researchers unravel the social network of immune cells

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>