Characteristics of aerosols over Beijing and Kanpur derived from the AERONET dataset

Beijing and Kanpur are two cities identified as high aerosol optical thickness (AOT) and complex composition of aerosols in Asian monsoon regions. Detail knowledge of key aerosol types in these two countries would be helpful for clarifying the mechanisms of aerosol radiative forcing and improving the accuracy of satellite remote sensing in these two countries. This study examines the characteristics of aerosol types over Beijing and Kanpur derived from a 12-year dataset from Aerosol Robotic Network (AERONET) stations and compares them via cluster analysis of optical and microphysical properties. Aerosols in Beijing are more complex than in Kanpur. Four fine-size dominated aerosol types (including two types of moderately absorbing aerosols, one highly absorbing aerosol type and one non-absorbing aerosol type) and one coarse-size dominated aerosol type are identified over Beijing. In Kanpur, two fine-sized dominated aerosol types (one high absorbing aerosol type and one non-absorbing aerosol type) and one coarse-sized dominated aerosol type are obtained. Compared to Beijing, the average SSAs of non-absorbing and high-absorbing aerosols are lower for the four wavelengths (440 nm, 676 nm, 869 nm, 1020 nm) in Kanpur. High absorbing aerosols usually occur in the months December to February (DJF) for both sites. The proportion in Kanpur (14%) is about twice that in Beijing (7%). Non-absorbing aerosols are usually observed in the months June to August (JJA) for both sites. Their proportion in Kanpur (31%) is ∼3 times larger than that in Beijing (11%). Coarse aerosols are frequently observed in the months March to May (MAM) for both sites. Their proportion in Kanpur (54%) is two times larger than in Beijing (21%).