1994 Volume 29 Issue 4 Pages 179-195
Wintertime high concentration of NO2 was analyzed by using a two-dimensional meso-scale numerical model and an Eulerian type atmospheric diffusion model (photochemical grid model) which includes photochemistry. A typical local wintertime circulation was simulated, and together with typical emission strengths from the central Tokyo was used for the analysis of representative wintertime pollutant characteristics. The NO2 formation nudget (ppb/min) (contributions from atmospheric diffusion and chemical reactions) was examined. The results show that all of the increase in NO2 concentration is due to chemical reactions with the latter peaking at about 1030 JST and 1630 JST. These peaks are stronger than the decrease due to the atmospheric diffuion (meteorological terms) and results in an increase of NO2 concentration at these times. Detailed data analysis show that the chemical contribution from the HO2+NO→NO2 reaction is important in the morning hours, while the NO+ O3→NO2 reaction plays an improtant role after 1400 JST. A sensitivity analysis by changing the source emission intensities for NMHC and NOx is also included. The nonlinear relationship between NO2, max, O3, max and emission intensities was analyzed. It is found that the individual controls on NOx and NMHC are a strongly non-linear on NO2, max (i. e. a 30% reduction gives only a 18% decrease in NO2, max). The simultaneous reduction of NOx and NMHC shows a 1: 1 relationship between NO2, max and emission strength.
