干旱区生态环境知识资源中心

The Aihui-Tengchong Line or the internationally known "Hu Line" divides China into the east and west parts, based on differences in China's population, geography, climate and economy, all of which are closely associated with the aerosols over China. By using the aerosol optical depth (AOD) data of MODIS during years 2000-2010, the geographical and climatological distributions of aerosols over China are presented, and the "Hu Line" is found also to describe a geographic division of aerosols over China: on the east part, the monthly AOD varies from the peak (>0.5) during March and June to the low of around 0.3 in November and December with an annual mean of about 0.45, mostly contributed by anthropogenic aerosols from the human activities; on the west part, the AOD is dominated by the naturally emitted aerosols with an annual mean of 0.25 changing between the high (about 0.3) in the period of April to July and the low (<0.2) from October to January. The positive and negative trends in annual AOD over 2000-2010 are respectively found in the regions on the east and west. Asian monsoon has a notable impact on the interannual variability of aerosols over the east region by modulating the atmospheric transport and precipitation washout. The interannual aerosol variations in the west are strongly influenced by dust emission sources in the deserts. The dust weather processes control the natural dust emissions. The maximal AOD of 0.3 in the west China could be brought by the frequent dust storm events.