Aerosol absorption characteristics over 23 AERONET locations

Abstract

Based on AERONET measurements, aerosol absorption properties over 23 AERONET sites are analyzed. The properties include aerosol single scatter albedo (SSA), correlation characteristic of SSA with aerosol optical thickness (AOT), absorption optical thickness and absorption wavelength index. The index is introduced to indicate wavelength-dependence of absorption optical thickness. Among the 23 sites, 8 sites locate over Asia, 3 over Africa, and 12 in USA. Some results are summarized as follows: 1)Total mean absorption optical thickness for the 440nm-wavelength changes between 0.0061 (Howland, USA) and 0.0939 (Beijing, China), and it ranges from 0.0019 (Howland) to 0.0457 (Yulin, China) for the 1020nm wavelength. There are three peaks of absorption optical thicknesses, locating over China, India and north-Africa, respectively. 2)Over all sites except for two sites (Goa-india in India and Dahkla in Africa), correlative coefficients between SSA and AOT are positive, changing from 0.048 to 0.692. This characteristic implies that relative contribution of stronger-absorbing aerosol component to total AOT decreases when the AOT increases. In other hand, correlative coefficients between Angtrdm index and AOT are usually negative, showing trendily increasing contribution to total AOT from larger particles when the AOT increases. 3)Apart from two sites of Dahkla and Ilorin in Africa, absorption wavelength index is 0.09-1.29 less than Angtrdm index, the smallness being larger for some sites in USA. Usually, the larger Angtrdm index is, the stronger the smallness.