2013 Volume 33 Issue 4 Pages 298-307
Air pollution is a social and transboundary environmental issue, and pollution-related problems are especially acute in China. With the rapid growth of the Chinese economy, massive sulfur oxide (SOx) and nitrogen oxide (NOx) air pollution is caused by fossil fuel consumption in the new “automobile society.” These airborne pollutants are transported by strong seasonal winds from source regions in China to neighboring countries, and they cause acid rain and photochemical smog.
To deal with this problem, extensive observation by atmospheric observatories is essential. Several computer simulations using atmospheric models have also been developed. Remote sensing technology is useful for the near real-time monitoring of air pollutants, and the interpretation of moderate-resolution imaging spectroradiometer (MODIS) true-color images is a common technique for conducting the real-time monitoring of air pollutants. However, there are some difficulties in the MODIS decision process, particularly in discriminating between air pollutants and clouds.
To overcome this problem, we propose a new MODIS false-color composite image method that is created by an aerosol enhancement (AE) reflectance index and a water index (WI). The false-color image distinctly depicts, in yellow, the air pollutants that are greater than 0.4 in aerosol optical thickness. In a case study of transboundary air pollution in February 2011, the movement of air pollutants was clearly understood when we conducted a time-series analysis of MODIS false-color images, a chemical analysis of the rimes of tree samples collected from Japan’s Mount Zao, and a data analysis of some atmospheric observatories in Yamagata Prefecture, Japan. The results confirmed that the air pollutants were transported by a strong wind from the North China Plain to Mt. Zao, and our findings confirmed that the proposed method employing false-color composite images is useful for monitoring and predicting transboundary air pollution.
