Abstract
A model inter-comparison of secondary pollutant simulations over urban areas in Japan, the first phase of Japan’s study for reference air quality modeling (J-STREAM Phase I), was conducted using 32 model settings. Simulated hourly concentrations of nitric oxide (NO) and nitrogen dioxide (NO2), which are primary pollutant precursors of particulate matter with a diameter of 2.5 µm or less (PM2.5), showed good agreement with the observed concentrations, but most of the simulated hourly sulfur oxide (SO2) concentrations were much higher than the observations. Simulated concentrations of PM2.5 and its components were compared to daily observed concentrations by using the filter pack method at selected ambient air pollution monitoring stations (AAPMSs) for each season. In general, most models showed good agreement with the observed total PM2.5 mass concentration levels in each season and provided goal or criteria levels of model ensemble statistics in warmer seasons. The good performances of these models were associated with the simulated reproducibility of some dominant components, sulfates (SO42−) and ammonium (NH4+). The other simulated PM2.5 components, i.e., nitrates (NO3−), elemental carbon (EC), and organic carbon (OC), often show clear deviations from the observations. The considerable underestimations (approximately 30 µg/m3 for total PM2.5) of all participant models found on heavily polluted days with approximately 40–50 µg/m3 for total PM2.5 indicated some problems in the simulated local meteorology such as the atmospheric stability. This model inter-comparison suggests that these deviations may be owing to a need for further improvements both in the emission inventories and additional formation pathways in chemical transport models, and meteorological conditions also require improvement to simulate elevated atmospheric pollutants. Additional accumulated observations are likely needed to further evaluate the simulated concentrations and improve the model performance.
Highlights
Particulate matter (PM) consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the atmosphere
As mentioned in Section 2.2., most of the participants employed the baseline meteorological fields; other chemical transport model (CTM) (M07, M20) used WRF-Advanced Research WRF (ARW) outputs based on their own conditions, including physical options, parameterizations, and a fine input meteorological analysis data, which is the grid point value derived from the mesoscale model (GPV MSM) data by Japan Meteorological Agency (JMA)
Major gaseous pollutants were monitored at the ambient APMSs (AAPMSs)
Summary
Particulate matter (PM) consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the atmosphere. Water-soluble PMs affect the regional climate system interacting with cloud microphysics. These radiative and microphysical interactions can induce changes in regional precipitation and atmospheric circulation patterns. Combining the regional three-dimensional chemical transport model (CTM) with comprehensive particulate formations may be a useful tool for understanding the detailed behavior of short-lived PM2.5 components in the atmosphere. The urban air quality model inter-comparison study in Japan (UMICS) series [10,11,12]. A model inter-comparison framework, Japan’s study for reference air quality modeling (J-STREAM), was designed to establish a reference regional CTM system to consider strategies for reducing PM2.5 and its relevant substances [5]. The model improvements will be discussed based on the inter-model differences
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