Abstract: Based on the data of atmospheric pollutants and the corresponding meteorological observation data from 2002 to 2011 in Xi’an, the temporal and spatial distributions of air pollution and its relationship with meteorological conditions were analyzed. The typical upper-level circulation situation in the day when air quality is superior grade or above light pollution grade, forming reasons and transport path of pollutants were discussed. The results indicate that the primary pollutant is PM₁₀ in Xi’an, and its maximum concentration appears in winter during heating period. Rainfall is the significant wet scavenging effect for pollutants, and air quality status has obvious continuity owing to the continuity of weather system. Presence of inversion temperature and decrease of the maximum mixed layer height make atmospheric stratification stable and wind speed small, hinder the convective movement of air, which lead to the weak diffusion of pollutants along the vertical direction. Thus, it is not favorable to the diffusion of pollutants, and it easily makes the ambient air quality descended.

Key words: font-family: "Times New Roman", mso-font-kerning: 1.0pt, mso-ansi-language: EN-US, mso-fareast-language: ZH-CN, mso-bidi-language: AR-SA, Pollutant')">mso-fareast-font-family: 宋体">Pollutant, Wet scavenging, Air pollution