Outline

Hajime Akimoto and Oliver Wild of the Atmospheric Composition Research Program, Frontier Research System for Global Change, a project run by the Japan Agency for Marine-Earth Science and Technology (an independent administrative institution) have found using model experiments that ozone formed over source regions upwind of East Asia, such as North America and Europe, is transported over the Eurasian continent and affects oxidant concentrations over Japan.

This research was published in the June issue of the Journal of Geophysical Research by the American Geophysical Union.

Background

The problems associated with trans-boundary transport of atmospheric pollution at a regional scale, such as acid rain, have long been recognized. However, it is now becoming clear that inter-continental long-range transport of atmospheric pollutants on a hemispheric scale from Europe to Asia, from Asia to North America, and from North America to Europe, are also a serious environmental issue. It is well known that one trans-boundary pollutant from China, ozone (note 1), a major atmospheric oxidant (note 2) and a precursor of photochemical smog, has a significant effect on oxidant concentrations over Japan. The Frontier Research System for Global Change has been conducting research which suggests that studies of oxidants over Japan should include the effects of inter-continental transport from North America and Europe in addition to trans-boundary pollutant transport from China.

Output

Based on the results of model experiments(on an SX-5 supercomputer,Note 3)using a global chemical transport model (FRSGC/UCI CTM,Note 4)which calculates both photochemical and transport processes(reference 1),it is found that ozone formed over source regions upwind of East Asia, such as North America and Europe, is transported over the Eurasian continent and affects oxidant concentrations over Japan(Figures1, 2, 3). The maximum ozone pollution transported from Europe is about 2-3 ppb at the surface, and about 4-5 ppb in the upper troposphere. It is also found that the amount of ozone transported from North America is about the same as that from Europe, despite the much greater transport distance over Eurasia to Japan, and may be even more in Winter to Spring (Note 5). This research indicates that oxidant concentrations from Europe and North America together increase the concentration of surface ozone in Japan by a few ppb, and may make a significant contribution to exceedance of Japan’s environmental standard of 60 ppb.

Contacts

Frontier Research System for Global Change
Contact: Ms. Ota
Tel: +81 (0)45-778-5687 (direct)
Homepage: http://www.jamstec.go.jp/frcgc/eng/index.html
JAMSTEC, Public Relations Office, General Affairs Department
Tel:+81 (0)46-867-9066
Homepage: http://www.jamstec.go.jp/

Note 1:
Ozone: In the stratosphere, oxygen atoms (O) formed in the photolysis of oxygen (O2) by ultraviolet (UV) light from the sun produce ozone (O3). This ozone is in turn photolyzed to regenerate O and O2 by absorbing UV light, which is harmful to living things on Earth. However, in the troposphere (lower atmosphere), the focus of this study, ozone is a major component of photochemical smog and is an air pollutant toxic to living things. It is produced from oxygen atoms formed by the photolysis of nitrogen dioxide (NO2) emitted from automobiles and factories. According to the IPCC Third Assessment Report (2001), ozone is recognized as the third most important greenhouse gas following carbon dioxide and methane.

Note 2:
Oxidants: Collective term for the oxidizers (oxidizing agents) in the atmosphere which are the cause of photochemical smog. Nitrogen Oxides (NOx) and Hydrocarbons (HC) emitted from factories and automobiles are photolysed (split up) by ultraviolet light from the sun, and form oxidizing agents such as ozone (the main component, 90%), peroxyacetyl nitrate (PAN) and hydrogen peroxide. High concentrations of oxidants lead to the formation of photochemical smog, which causes damage to human health and to plants.

Note 3:
Global Chemical Transport Model (FRSGC/UCI CTM): FRSGC’s improved version of a global three-dimensional chemical transport model developed at the University of California, Irvine, incorporating photochemical oxidation schemes. It simulates the emission, atmospheric transport, chemical conversion and removal of precursor pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC), and calculates the formation and global distribution of ozone and other oxidants.

Note 4:
Super-high-speed supercomputer owned by FRSGC. It adopts state-of-the-art super-high speed and high accumulation CMOS technology. The SX-5 fuses shared memory with a decentralized memory architecture. As it can be used efficiently for science and technology applications, it is used at FRSGC for process research at global scales. With a rich RAS feature, it allows rapid and prompt error diagnosis and easy preventive protection which increase total reliability, availability,and serviceability.

RAS: Reliability, Availability, Serviceability
CMOS: Complementary Metal Oxide Semiconductor

Note 5:
The reason is that while ozone from Europe is predominantly transported near the surface and a fairly large amount is removed, ozone from North America is transported in the upper troposphere over the Atlantic where its lifetime is much longer.