Minimizing light absorption measurement artifacts of the Aethalometer: evaluation of five correction algorithms

Abstract

The aerosol light absorption coefficient is an essential parameter involved in atmospheric radiation budget calculations. The Aethalometer (AE) has the great advantage of measuring the aerosol light absorption coefficient at several wavelengths, but the derived absorption coefficients are systematically too high when compared to reference methods. Up to now, four different correction algorithms of the AE absorption coefficients have been proposed by several authors. A new correction scheme based on these previously published methods has been developed, which accounts for the optical properties of the aerosol particles embedded in the filter. All the corrections have been tested on six datasets representing different aerosol types and loadings and include multi-wavelength AE and white-light AE. All the corrections have also been evaluated through comparison with a Multi-Angle Absorption Photometer (MAAP) for four datasets lasting between 6 months and five years. The modification of the wavelength dependence by the different corrections is analyzed in detail. The performances and the limits of all AE corrections are determined and recommendations are given

The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

“…For the TFE-coated glass filter we obtained C ≈ 1.57 using the 2-week Klagenfurt campaign data, assuming C = 2.14 for quartz filter (Weingartner et al, 2003). There is some uncertainty with this value since values of C for quartz filter as obtained by comparisons with other techniques differ (Weingartner et al, 2003;Collaud Coen et al, 2010;Müller et al, 2011a, Segura et al, 2014.…”

“…All filter-based optical methods exhibit loading effects (Bond et al, 1999;Weingartner et al, 2003;Virkkula, 2010;Virkkula et al, 2005Virkkula et al, , 2007Collaud Coen et al, 2010;Park et al, 2010;Hyvärinen et al, 2013). The relationship between attenuation and BC surface loading is linear for low attenuation values.…”

“…The enhancement parameter C has no statistically significant spectral dependence (Weingartner et al, 2003;Segura et al, 2014), with its value determined by comparing different methods and instruments in laboratories and in ambient observatories (Weingartner et al, 2003;Collaud Coen et al, 2010;Müller et al, 2011a;Segura et al, 2014), resulting in a range of values. The value of C may depend on the particle properties, as shown for the particle soot absorption photometer (PSAP) (Nakayama et al, 2010).…”

Black and brown carbon over central Amazonia: Long-term aerosol measurements at the ATTO site

“…The correction applied in this study has been described in a previous article (Saturno et al, 2016). The compensation algorithm is based on the correction scheme proposed by Collaud Coen et al (2010). It uses MAAP data as a reference absorption measurement, which could introduce uncertainties related to the modification that aerosol particles can suffer by being deposited on a filter matrix.…”

Seasonality of aerosol optical properties in the Arctic

“…Collaud Coen et al, 2010;Drinovec et al, 2015), including GAW recommendations for the AE31 contained in…”