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Figure 1. Hourly time series of O3 NO, NO2, CO and PM1O for the two experiments are shown for three stations: Lernwu, Zhaoin and Chaochou.

resolution of the model decreases from 2 m near the surface to 1 km at a 12 km altitude. Species with a photochemical lifetime shorter than 10 min are calculated by neglecting the transport. The time step for model integration for transport and chemistry is 30 s. Initial vertical distributions of trace species are prescribed by assuming constant mixing ratios equal to observed values in the mixed layer. The initial values of short-lived species in the mixed layer are not important to the model results, because emissions and photochemistry quickly redefine the concentrations after a few days of model simulations. Above the mixed layer, mixing ratios of trace gases are assumed to be negligible except for CO and O3, which are assumed to be their observed seasonal average values. The value of the eddy diffusion coefficient (Kz) in the surface layer is calculated from the similarity theory (Trainer et al., 1987). The value of Kz above the surface layer is specified to be 60ms-2. Dry deposition and heterogeneous removal processes are included in the same way as in Trainer et al. (1987). The surface resistance is set at 2s/cm for O3 and peroxides, 0.1s/cm for HNO3 and 3.3s/cm for carbonyls and organic nitrates. Lifetimes of heterogeneous losses of soluble gases HNO3, H2 O2, ROOH,

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