GAW Report No. 205 - IGAC Project

CHAPTER 3 - ASIAFigure 58 - Annually averaged PM2.5 concentrations observed by the Taper Elemental Oscillation Method at roadside, urban,and suburban stations [Ministry of the Environment of Japan, 2009]. The numbers of each type of measurement site inJapan and the Kanto area are given in the textFigure 59 - Fine and coarse aerosol concentrations observed at an urban background site in Tokyo. Reproduced bypermission of Elsevier from Minoura, H., K. Takahashi, J. C. Chow, and J. G. Watson (2006), Multi-year trend in fine andcoarse particle mass, carbon, and ions in downtown Tokyo, Japan [Minoura et al., 2006]Research projectIntegrated Measurement Programme for Aerosol and oxidant Chemistry in Tokyo (IMPACT)campaigns were conducted within the framework of the International Global Atmospheric ChemistryProject (IGAC), Mega-Cities: Asia. The background, objectives, methodology, and importantfindings of the IMPACT campaigns are presented in Chapter 7.Remaining problemsAccording to the Tokyo Metropolitan Government (2005), the observed increase in thefrequency of high-O 3 days over Tokyo cannot be explained by year-to-year variations inmeteorological parameters, such as solar radiation and temperature. Thus, improved understandingof the factors controlling O 3 concentrations is needed to assess effective ways to lower the levels ofphotochemical pollution over Tokyo, which requires more detailed studies of the relationships of O 3concentrations with its precursors’ emissions in various areas.126