Graphical aerosol classification method using aerosol relative optical depth

A simple graphical method is presented to classify aerosol types based on a combination of aerosol optical thickness (AOT) and aerosol relative optical thickness (AROT). Six aerosol types, including maritime (MA), desert dust (DD), continental (CO), sub-continental (SC), urban industry (UI) and biomass burning (BB), are discriminated in a two dimensional space of AOT440 and AROT1020/440. Numerical calculations are performed using MIE theory based on a multi log-normal particle size distribution, and the AROT ranges for each aerosol type are determined. More than 5 years of daily observations from 8 representative aerosol sites are applied to the method to confirm spatial applicability. Finally, 3 individual cases are analyzed according to their specific aerosol status. The outcomes indicate that the new graphical method coordinates well with regional characteristics and is also able to distinguish aerosol variations in individual situations. This technique demonstrates a novel way to estimate different aerosol types and provide information on radiative forcing calculations and satellite data corrections. •A simple graphical method is developed to classify aerosol types.•The method uses aerosol optical thickness and aerosol relative optical thickness.•Six aerosol types discriminated in a 2D space of AOT440 and AROT1020/440.•AROT ranges for each aerosol type determined through numerical calculations.•The method is able to distinguish aerosol variations in individual situations.