September 14, 2009 | In 2006, a team of NCAR researchers convened in Mexico City for MIRAGE (Megacity Impacts on Regional and Global Environments), a study of the chemical and physical transformation of air pollution in urban areas and its impact on air quality, ecosystems, and climate.

Another MIRAGE field campaign kicks off this month, this time in Shanghai, China's largest city. The three-week project is the first of a series of campaigns, with researchers currently looking at ozone formation. A larger campaign being planned for May 2011 is expected to include participants from a larger number of U.S. and Chinese universities. It will focus on interactions between regional ecosystems and large cities and the impact of economic development on the atmosphere.

Shanghai provides scientists with an ideal site for studying how the transition from a developing to developed economy affects urban environments. With about 20 million inhabitants, the city has almost doubled in population in the last 20 years. Like other cities in eastern China, Shanghai experiences severe air pollution, with aerosol concentrations often measuring four to five times higher than in American cities. The region is also heavily reliant on coal burning for energy, which affects the chemistry of ozone production. It is surrounded by a cluster of large cities that are expected to grow into mega cities of their own.

The researchers will establish a network of measurements in Shanghai to study ozone and its precursors. Some of their goals include applying and evaluating WRF-Chem (the Weather Research and Forecasting coupled with a model for air quality and chemistry), developing a chemical weather forecasting system for Shanghai, and studying oxidant and aerosol processes at the urban to regional transition.

"Eastern China is a very important region for studying the impacts of air pollutants on air quality and climate on not only regional but also global scales," says NCAR scientist Xuexi Tie. "However, there is a lack of comprehensive studies in the region. The planned field campaigns will provide important information for a better understanding of the influences of the growth of megacities on atmospheric environments."

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