Uncertainties propagated from optical properties in aerosol classification schemes

ARIEL SCAGLIOTTI; JOSEFINA URQUIZA; SEBASTIAN DIEZ

On - line

Congreso; 16th IGAC Scientific Conference Atmospheric Chemistry from a Distance: Real Progress through Virtual Interaction; 2021

nternational Global Atmospheric Chemistry (IGAC) Project

Aerosol Optical Depth (AOD) is an integrated measurement of light extinction in the atmospheric column due to the presence of aerosols. Surface sun photometers, such as those managed by the AERONET network (AErosol RObotic NETwork), measure AOD and other aerosols optical properties. Continuous observations of AOD at different wavelengths can be used to derive other products, but the uncertainties associated with the instrument and the acquisition and control algorithms are then propagated affecting these products such as the Ångstrom coefficient. This parameter is of special importance as it is used for aerosol classification, whose results are usually reported without considering the uncertainty propagation impacts. In terms of relative errors, the impact is greater when the absolute value of AOD is lower. Furthermore, if it is also taken into account that the limits proposed by various authors for aerosol classification are usually vague, the conclusions that can be extracted from must be observed with extreme caution. This work aims to characterize the effect of such uncertainties on the aerosol classification schemes using as a study case the Metropolitan Area of Buenos Aires in Argentina, where relatively low AOD values are observed during the year. In this work it was possible to determine that the Ångstrom coefficient calculated as the slope of the spectral dependence of the AOD in a logarithmic space has a mean propagated relative uncertainty of around 30% and that the classifications made with the different schemes are highly affected by this uncertainty.