Abstract:The characteristics of aerosol optical depth (AOD) and Angstrom wavelength exponent (α) were analyzed and compared using Cimel sunphotometer data from 2011 to 2012 at national basic meteorological station in Hangzhou city of China. The results showed that the mean value of AOD500nm and α440-870nm were 0.86±0.47and 1.25±0.23, respectively. The averaged AOD over Hangzhou had no obviously seasonal variation characteristics. It was closely related to the weather patterns and internal and external sources influence in this region. The seasonal variation of α was not distinct. Due to dust aerosol spreading from north of china, the α measured in spring was a little lower compared to other seasons. The diurnal variation of averaged AOD showed a single peak distribution with the peak value and valley value at 15:00 and 06:00 respectively. The significantly increased value of AOD in the afternoon were due to the secondary aerosols generated from photochemical reactions that caused by strongly solar radiations and the aerosols in the surface layer spreading to upper layer influenced by turbulent transfer action. Both the AOD and α showed obvious single peak of frequencies based on the frequency distribution. It was found that the AOD and α can be better characterized by a lognormal distribution. The frequency of α, occurring in the high value range between 1.1and 1.7was 77.8%, which indicated that the average effective radii of aerosol particles were small and the aerosols should be classified as urban-industrial aerosols in Hangzhou. The data also showed high AOD(>1.0) both clustering in the fine mode growth wing and the coarse mode.