Toyota Develops Tropospheric Ozone-concentration Simulator

Toyota City, Japan - Toyota Motor Corporation (TMC) and Toyota Central R&D Labs., Inc., have developed a simulator able to predict tropospheric ozone concentrations across the whole of South and East Asia. The project was carried out in collaboration with Tsinghua University in China1, The Energy and Resources Institute (TERI) in India2, and the International Institute for Applied Systems Analysis (IIASA) in Austria3. The simulator is expected to contribute with efforts to reduce energy consumption and limit emissions of the substances in South and East Asia that cause atmospheric pollution—one factor in global warming—and thereby bring about significant benefits worldwide.

1. Tropospheric ozone characteristics, measures necessary to reduce concentrations
Well known is the ozone layer in the stratosphere (starting at a height of approximately 10 km), which protects the earth’s ecosystem by absorbing ultraviolet rays. Less known is the ozone in the troposphere, which extends to approximately 10 km above the earth’s surface. The tropospheric ozone is the main cause of photochemical smog, an atmospheric pollutant harmful to human health and plant growth. It is also one of the greenhouse gases that contributes to global warming and as such comes next in line as a target for reduction in concentration after CO2 and methane.

Predicting tropospheric ozone concentrations is difficult because tropospheric ozone is not emitted directly into the atmosphere but formed in the atmosphere by photochemical reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOC) emitted from a range of sources. As these photochemical reaction pathways are very complex, reduction of NOx and VOC emissions may not necessarily be effective in reducing tropospheric ozone concentrations. To predict tropospheric ozone concentrations, it is necessary to account for the complex photochemical reactions taking place in the atmosphere as well as NOx and VOC emissions data.

2. Simulator development: Joint research background and objectives
With economic growth in developing Asian countries and a resulting increase in tropospheric ozone caused by consumption of various forms of energy on a large scale, there is concern over environmental deterioration on both a local and global level. This has led to calls for reductions in emissions of atmospheric pollutants, including those from motor vehicles.

Toyota sought a way of reducing tropospheric ozone concentrations to help address the problem across the whole of South and East Asia. Toyota collaborated with facilities in various countries to undertake research on the prediction of tropospheric ozone concentrations with the aim of contributing to a strategy for lessening their effects on human health and plant growth.

3. Method used by simulator and role of each facility in joint research program
To improve accuracy, the simulator developed in the research project combined:
1) Energy consumption under current conditions and projected energy consumption based on future energy policies for each of the countries in South and East Asia;
2) CO2, NOx, and VOC emissions;
3) a three-dimensional air quality model that predicts tropospheric ozone concentrations, while taking meteorological conditions into account.

For South and East Asian countries other than China and India, the data in 1) and 2) above were prepared by IIASA and based on scenarios supplied by the International Energy Agency (IEA). For China and India, where marked economic development is expected to continue, detailed databases for their respective regions and sectors were prepared by Tsinghua University for China and by TERI for India and referenced government energy and environment policy.

The model in 3) above takes account of complex photochemical reactions based on NOx and VOC emissions with meteorological conditions also factored in to predict tropospheric ozone concentrations accurately to the hour or less. Tropospheric ozone can move unhindered across national boundaries. To predict tropospheric ozone concentrations across the whole of South and East Asia, the Toyota Central R&D Labs assembled detailed data from each country on energy consumption and NOx and VOC emissions to construct a simulation based on a three-dimensional air quality model. For China and India, both needing more detailed prediction data to reflect economic development going forward, the simulator can predict tropospheric ozone concentrations centered mainly on the area near the respective country.

4. Expected simulator benefits
The simulator incorporates energy consumption that takes into account future energy policies that are currently under consideration and can predict tropospheric ozone concentration throughout South and East Asia. The main benefit of the simulator is the ability to comprehensively investigate policies needed for tropospheric ozone reduction, CO2 reduction scenarios and atmospheric improvement scenarios.

Investigation of strategies to reduce atmospheric pollution in major cities has already begun in China. Meanwhile, it has been indicated by the United Nations Environment Programme (UNEP) that reduction of tropospheric ozone would be effective in suppressing short-term rises in temperature, suggesting that the simulator could be useful in exploring strategies for limiting climate change.

Looking ahead, Toyota hopes the simulator will be used widely across the various countries and regions of South and East Asia, and in this way contribute to formulating effective energy policies that combine reduction of energy consumption and CO2 emissions with a limitation of tropospheric ozone concentrations.

A two-day "International Workshop" will be held at Tsinghua University in China on May 26 and 27 to share information concerning the simulator. Researchers from collaborating institutions, as well as from other institutions around the world seeking to address atmospheric pollution, are scheduled to attend to discuss ways to further promote research and implement policy.


1Established in 1911, one of China’s leading universities. Approx. 3,000 professors and associate professors approx. 36,000 students.
2Established in 1974, one of India’s leading research institutions. Approx. 900 researchers. Director-General, Rajendra Pachauri, is chairman of the Intergovernmental Panel on Climate Change (IPCC).
3International research institute established in 1972 in Austria. Approx. 200 researchers.