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This page contains Press Releases of 2 Dec. from:
Note by me (JvG): the title of the ESA Press Release uses "ozone hole", but that should not really be used, as it is only a "mini hole" so to say. |
Deze pagina bevat Persberichten van 2 Dec. van:
Opm. door mij (JvG): de titel van het ESA-Persbericht gebruikt de term "ozongat", maar dan zou eigenlijk niet gebruikt moeten worden, aangezien het maar om een "mini-gat" gaat, zogezegd. |
===> Tekst van enige krantenartikelen (Dutch)
<=== Northern Hemishphere ozone values
Persbericht KNMI/ESA 2 december 1999 KS 99/10
Op 30 november j.l. heeft het GOME instrument aan boord van de
satelliet ERS-2 van de Europese ruimtevaart organisatie (ESA)
bijzonder lage ozon waarden gemeten boven Nederland, Engeland en
Scandinavie. Metingen vanuit het KNMI in De Bilt gaven waarden
van 198 DU aan, terwijl 290 DU normaal is voor de tijd van het jaar.
Mini ozongaten boven Europa komen van tijd tot tijd voor. De laatste was eind 1997. Het mini-gat van 30 november is van belang, niet alleen omdat het record "lage ozonwaarde" gebroken is, maar ook omdat het onmiddellijk gedetecteerd is door de satellieten die de ozonlaag constant in de gaten houden.
De lage ozonwaarden worden vermoedelijk veroorzaakt door een opstapeling van drie effecten:
Deze lage ozonwaarden zijn echter een locaal fenomeen, en niet typisch voor het hele Noordelijk Halfrond, of het Noordpoolgebied. Elders, zoals boven Canada en Alaska waren de ozonwaarden vrij hoog, rond de 400 DU. Gemiddeld over het noordelijk halfrond is de ozonlaag dit jaar normaal ontwikkeld.
Het Europese "Global Ozone Monitoring Experiment" (GOME) satelliet instrument meet het zonlicht dat door de aarde weerkaatst is. Uit de absorptie van het ultraviolette zonlicht kan de hoeveelheid ozon in de atmosfeer berekend worden.
GOME is een van de instrumenten aan boord van ERS-2 aardobservatiesatelliet. De satelliet wordt beheerd door ESA. De ozonwaarden worden berekend met de "Fast Delivery Service" van het KNMI.
In Europa wordt inmiddels gewerkt aan de volgende generatie satellietinstrumenten voor het waarnemen van ozon en andere chemicalien in de atmosfeer. De Envisat satelliet, ontworpen en gebouwd door 14 Europese landen van de ESA zal in 2001 gelanceerd worden, en zal drie ozon instrumenten bevatten. ESA en EUMETSAT (European Organisation For The Exploitation Of Meteorological Satellites) werken aan een serie meteorologische satellieten (METOP) die een verbeterde versie van het GOME instrument aan boord hebben, zodat het monitoren van de ozonlaag van 2004 tot 2014 door kan gaan. Tevens wordt er gewerkt aan een Nederlands "Ozone Monitoring Instrument" (OMI) aan boord van de NASA satelliet EOS-chem.
<=== Northern Hemishphere ozone values
ESA Press Release No. 47-99 -- Paris, 2 December 1999
On Tuesday 30 November 1999 the European Space Agency's ERS-2 remote sensing
satellite detected abnormally low ozone levels over north western Europe.
Above the UK, Belgium, Netherlands and Scandinavia ozone levels were nearly
as low as those normally found in the Antarctic. Individual point
measurements made from the ground in the Netherlands confirm that local
values were almost 2/3 of the normal level at this time of year.
The ozone layer protects our planet from potentially harmful ultraviolet sunlight. A thinning in the ozone layer results in an increase of the amount of ultra-violet radiation. At this time of the year at our latitudes, however, the sun does not rise high enough above the horizon to deliver a significant amount of harmful ultraviolet light.
Mini-ozone holes over Europe are of increasing scientific interest with relevance in the political debate. The previous one was detected in 1997. Tuesday's event is significant not only because of the low levels reached, but also because it was immediately detected by European satellites which are monitoring the entire globe.
Scientists world-wide are studying the exact causes of these ozone lows. They know that these are often associated with exceptionally low temperatures in the lower stratosphere and the presence of polar stratospheric clouds, which contain catalysts which speed up the chemical reactions that destroy ozone.
Since the launch of ERS-2 in 1995 Europe is equipped with its own space-borne ozone monitoring instrument, the Global Ozone Monitoring Experiment (GOME). European expert teams have been using this instrument to produce daily maps of the global ozone layer, and make them available to the public on the world-wide web. This recent ozone low was first drawn to ESA's attention by a team working at the Royal Dutch Meteorological Institute (KNMI) in De Bilt (NL).
Europe is already preparing the next-generation of satellite instruments to improve the monitoring of ozone and other key chemicals in the atmosphere. ESA's environmental satellite Envisat, designed and built by European scientists and industry, will be launched in 2001 on an Ariane 5 launcher and will carry three new instruments to monitor atmospheric ozone, even more powerful than those carried on board ERS-2.
In addition, ESA and the European Organisation for the Exploitation of Meteorological Satellites, EUMETSAT, are preparing a series of three satellites (Metop) which will carry follow-on GOME instruments and will guarantee at least ten years continued monitoring of ozone from space from 2003 onwards.
<=== Northern Hemishphere ozone values
NASA Press Release No. 99-126 -- Dec. 2, 1999
"This is an extremely low measurement of ozone for the Northern Hemisphere," said Dr. Richard McPeters, Principal Investigator for Earth Probe TOMS. The measurement showed 165 Dobson Units (DU) over the North Sea between Scotland and Norway.
The previous low value of 167 DU was observed in the same region on Oct. 30, 1985. The lowest values of ozone in the Northern Hemisphere are typically seen in the late fall period. However, these low northern values rarely drop below 180 DU.
"A combination of stratospheric and tropospheric weather systems can occasionally create these extreme low ozone events," said Dr. Paul A. Newman of the NASA Goddard Space Flight Center in Greenbelt, Md. "We understand that dynamics can cause these low ozone events, but we're unsure why this event set a new record low value."
Scientists and others have a keen interest in polar ozone depletion. While this particular record low value results from a convergence of weather systems, severe depletions of ozone can result from chemical processes. The Antarctic ozone hole is an example of a large ozone loss caused by chemistry. Chemically caused Arctic ozone losses have also been observed, particularly in the Northern Hemisphere springs of 1996 and 1997.
This winter, NASA in collaboration with the European Commission, is staging the largest polar ozone campaign yet. The SAGE III Ozone Loss and Validation Experiment (SOLVE) is being conducted jointly with the European Commission sponsored Third European Stratospheric Experiment on Ozone (THESEO 2000). These collaborative campaigns will examine the processes that control polar and mid-latitude ozone levels at mid to high latitudes over the course of the Arctic winter. NASA Goddard has provided theoretical contributions, a high altitude light detection and ranging system for measuring ozone and temperature, and the operational support for some of the heavy lift balloons. Goddard scientists and instruments are integral parts of the SOLVE campaign being conducted this winter.
TOMS ozone data and pictures are available on the Internet at the following URL: http://ozoneaq.gsfc.nasa.gov/
More information about the U.S. SOLVE and European THESEO components (including a list of participating institutions) can be found at the respective web sites (SOLVE - http://cloud1.arc.nasa.gov/solve/ and THESEO 2000 - http://www.ozone-sec.ch.cam.ac.uk/).
TOMS-EP and airborne field programs are key parts of a global environmental effort of NASA's Earth Science enterprise, a long-term research program designed to study Earth's land, oceans, atmosphere, ice and life as a total integrated system. Goddard developed and manages the operation of the TOMS-EP for NASA's Office of Earth Science, Washington, D.C.
The TOMS instrument measures the total number of ozone molecules between the Earth's surface and space. The measurements units are Dobson units. Dobson units are convenient thickness measurements. The total ozone value represents the physical thickness of the ozone layer if all of those overhead ozone molecules could be brought down to the Earth's surface. The global average ozone layer thickness is 300 Dobson units, which equals three millimeters or 1/8th of an inch, and while not uniform, averages the thickness of two stacked pennies.
<=== Northern Hemishphere ozone values
<=== My post-doc. research at KNMI page
Jos van Geffen --
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