NASA鈥檚 Aura satellite has observed for the first time a link between local carbon monoxide levels and ozone levels close to Earth鈥檚 surface.
鈥淎ura is offering us a whole new way of looking at how pollution travels around the Earth, and precisely what the sources are,鈥� says Mark Schoeberl, project scientist for Aura at NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland, US. 鈥淭he better we understand the origins of pollution, the more public health stands to benefit, across borders.鈥�
Ozone in the upper atmosphere is beneficial, helping to block ultraviolet radiation from the Sun. But closer to the ground, in the troposphere, it is an air pollutant that can impair the body鈥檚 immune system or lead to an increased sensitivity to allergens.
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Ozone is the dominant component of smog, and one of the precursors for ozone formation is carbon monoxide. Now Aura鈥檚 Tropospheric Emission Spectrometer (TES) has allowed scientists to track the two gases as they move across land and ocean.
鈥淲hat TES provides us for the first time is evidence that carbon monoxide is associated [geographically] with the ozone pollution belt,鈥� says Daniel Jacob at Harvard University in Cambridge, Massachusetts, US, and a member of the TES team. Until Aura launched in 2004, scientists were limited in their ability to directly observe ozone in the troposphere.
Long-distance pollution
Aura鈥檚 observations also illustrate the fact that individual countries do not have complete control over their air quality, because ozone can travel across borders and even oceans. For example, the satellite鈥檚 observations show that ozone from eastern Asia crosses the Pacific Ocean and settles over California, contributing between 4 and 5 parts per billion (ppb) to the state鈥檚 air. Some ozone stems from industrial combustion, while seasonal brush fires release carbon monoxide.
California鈥檚 state-wide limit for ozone is 70 ppb over eight hours. With background levels being 40 ppb, the additional 4-5 ppb is significant, Jacobs says. Europe is also receiving similar levels of ozone from the US 鈥� about 5 ppb 鈥� as the winds blow the pollution eastwards over the Atlantic.
Existing computer models appear to be underestimating the pollution transported across the Pacific Ocean, Jacob told reporters at the American Geophysical Union conference in San Francisco, California, US, on Thursday.
In addition, the Ozone Monitoring Instrument on Aura has tracked the movement of the pollutant nitrogen dioxide across Europe, hour by hour.
Hole story
杏吧原创s also announced this week that Aura has determined that the seasonal ozone hole over Antarctica is slightly larger than in 2004, but smaller than in some previous years.
At its peak in September and October, the depleted area measured 9.4 million square miles (24.3 square kilometres). The largest hole ever, in 1998, covered 10.1 million square miles (26.2 square kilometres).
Since its launch, Aura has also provided the first global glimpse of the ice in clouds. Knowing how much ice is trapped in clouds should help scientists to determine the amount of solar energy reflected back into space and the amount bounced back to Earth鈥檚 surface.
Aura is part of the so-called 鈥淎-train鈥� of satellites, including NASA鈥檚 Aqua and the French space agency鈥檚 Parasol, which fly in formation as they monitor the
Earth. NASA aims to add the CloudSat and Calipso satellites to the constellation in 2006.