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Abstract:The inter-comparison of regional air quality models is an effective way to understand uncertainty in ambient pollutant concentrations simulated using various model configurations, as well as to find ways to improve model performance. Based on the outcomes and experiences of Japanese projects thus far, a new model inter-comparison project called Japan's study for reference air quality modeling (J-STREAM) has begun. The objective of J-STREAM is to establish reference air quality modeling for source apportionment and effective strategy making to suppress secondary air pollutants including PM 2.5 and photochemical ozone in Japan through model inter-comparison. The first phase focuses on understanding the ranges and limitations in ambient PM 2.5 and ozone concentrations simulated by participants using common input datasets. The second phase focuses on issues revealed in previous studies in simulating secondary inorganic aerosols, as well as on the three-dimensional characteristics of photochemical ozone as a new target. The third phase focuses on comparing source apportionments and sensitivities under heavy air pollution episodes simulated by participating models. Detailed understanding of model performance, uncertainty, and possible improvements to urban-scale air pollution involving secondary pollutants, as well as detailed sector-wise source apportionments over megacities in Japan are expected.

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Abstract. The spatial distribution of the source-receptor relationship (SRR) of sulfur over Northeast Asia was examined using a chemical transport model (RAQM) off-line coupled with a meteorological model (MM5). The simulation was conducted for the entire year of 2002. The results were evaluated using monitoring data for six remote stations of the Acid Deposition Monitoring Network in East Asia (EANET). The modeled SO 2 and O 3 concentrations agreed well with the observations quantitatively. The modeled aerosol and wet deposition fluxes of SO 2− 4 were underestimated by 30 % and 50 %, respectively. The domain was divided into 5 source-receptor regions: (I) North China; (II) Central China; (III) South China; (IV) South Korea; and (V) Japan. The sulfur deposition in each receptor region amounted to about 50-75 % of the emissions from the same region. The largest contribution to the deposition in each region was originated from the same region, accounting for 53-84 %. The second largest contribution was due to Region II, supplying 14-43 %. The spatial distributions of the SRRs revealed that subregional values varied by about two times more than regional averages due to nonuniformity across the deposition fields. Examining the spatial distributions of the deposition fields was important for identifying subregional areas where the deposition was highest within a receptor region. The horizontal distribution changed substantially according to season.