Impacts of the PBL Similarity on Concentrations and Dry Deposition Velocities of O3 and NOx

Spatial distributions of vertical eddy diffusivity (Kz)，dry deposition velocity(V), and concentrations of O3and NOxover East Asia are simulated using the surfacelayer similarity and the whole PBL similarity in the turbulence parameterization, after coupling the widely applied LLA (Lurmann Lloyd Atkinson) chemical mechanism in East Asia into the Regional Air Quality Eulerian Model (RAQM) and considering the temporal heterogeneity in rainwater in longterm modeling studies of air pollutants over a large domain. Simulations indicate that Kzvalues are significantly underestimated by the whole PBL similarity, with above 20% at 50 m and around 70% at 750 m high above the ground, respectively. Dry deposition velocities of O3 and NOx are underestimated at least 10% in the sea area on the east and south of Japan, while in the sea area on the east and west of Korea Peninsula the values are generally higher. Large deviations in Kzand dry deposition velocity between the two schemes lead to different results of O3 and NOx. Underestimation oKz values leads to large changes in NOx concentrations, with a maximum increase of 30% at 50 m high above the ground and approximately 5%-20% increases in mean NOxlevels in the whole PBL except the sea area on the northeast of Taiwan. However, the concentrations of O3 are dependent significantly on the dry deposition process. The surfacelayer similarity and the whole PBL similarity well depict the timing of O3and NOx peaks while the surfacelayer similarity follows observations in amplitude better than the whole PBL similarity. The surfacelayer similarity is a better choice than the whole PBL similarity and the first vertical model layer should be set within the surface constant flux layer even in longterm regional simulations of air pollutants.