How Earth’s air — and the material in our air — is shared around the world was recently illustrated by Dutch researchers who studied the patterns by which ozone travels geographically. A significant percentage of ozone at the tropospheric level is shared between countries, they found — low-level ozone is even shared in significant quantities between continents.

“Everything is connected,” Dr. Willem W. Verstraeten of theRoyal Netherlands Meteorological Institute and Wageningen University and lead researcher of the study, told the Speaker. “Local environmental air quality is not just a matter of taking local measures but is also a result of global activities international conventions — or the lack thereof.”

The recent work of Verstraeten and his colleagues focused on ozone in particular parts of the Earth’s troposphere, the region between the surface of the Earth and 12-20 kilometers above sea level.

“In our recent study we were looking at partial columns between 3 and 9 km (free troposphere). This is slightly different from surface ozone. At the surface most of it is produced locally or at short range.

At the level studied, ozone increases and decreases seasonally in the U.S., but levels vary significantly between the east and west of the country.

“For the U.S., generally spoken, the surface ozone measured at specific sites are slightly decreasing over eastern US and slightly increasing in the western part during summertime for the period 1990-2010,” Verstraeten told us. “During wintertime surface ozone tends to increase in both regions.”

Dr. Willem W. Verstraeten

Dr. Willem W. Verstraeten

The researchers also measured the patterns in which ozone is shared around the world. Due to the generally eastern flow of the atmosphere, the western states receive a lot of China’s ozone. In turn, ozone from America travels over the Atlantic ocean to Western Europe.

According to estimates, half of ozone in western Europe is imported from elsewhere,” noted Verstraeten, referring to past research on the subject. “More than a quarter originates from North America, almost 15% from the Asian continent and just 10% from the stratosphere.

Ozone around the world map

Another model study shows that for the western U.S. simulations indicate that ~10% of the surface ozone originates from Asia, for eastern US only ~1%. In the free troposphere it is higher — up to 10% and 15%, eastern USA and western USA respectively.

“These numbers depend on the used models and their respectively settings,” Verstraeten noted.

The report, “Rapid increases in tropospheric ozone production and export from China,” was completed by Drs. Willem W. Verstraeten, Jessica L. Neu, Jason E. Williams, Kevin W. Bowman, John R. Worden, and K. Folkert Boersma, and was published online in the journal Nature Geoscience.

By Justin Munce