Development of a new correction algorithm applicable to any filter-based absorption photometer

Abstract

Abstract. Among the various measurement approaches to quantify the light absorption coefficient (Babs), filter-based absorption photometers are dominant in monitoring networks around the globe. Numerous correction algorithms have been introduced to minimize the artifacts due to the presence of the filter in these instruments. However, from our recent studies conducted during the Fire Influence on Regional and Global Environments Experiment (FIREX) laboratory campaign, corrected filter-based Babs remains biased high by roughly a factor of 2.5 when compared to a reference value using a photoacoustic instrument for biomass burning emissions. Similar overestimations of Babs from filter-based instruments exist when implementing the algorithms on 6 months of ambient data from the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) user facility from 2013 (factor of roughly 3). In both datasets, we observed an apparent dependency on single-scattering albedo (SSA) and the absorption Ångström exponent (AAE) in the agreement between Babs based on existing correction factors and the reference Babs. Consequently, we developed a new correction approach that is applicable to any filter-based absorption photometer that includes light transmission from the filter-based instrument as well as the derived AAE and SSA. For the FIREX and SGP datasets, our algorithm results in good agreement between all corrected filter-based Babs values from different filter-based instruments and the reference (slopes ≈1 and R2≈0.98 for biomass burning aerosols and slopes ≈1.05 and R2≈0.65 for ambient aerosols). Moreover, for both the corrected Babs and the derived optical properties (SSA and AAE), our new algorithms work better or at least as well as the two common correction algorithms applied to a particle soot absorption photometer (PSAP). The uncertainty of the new correction algorithm is estimated to be ∼10 %, considering the measurement uncertainties of the operated instruments. Therefore, our correction algorithm is applicable to any filter-based absorption photometer and has the potential to “standardize” reported results across any filter-based instrument.

Effects of different correction algorithms on absorption coefficient – a comparison of three optical absorption photometers at a boreal forest site

“…In this study the PSAP data were corrected with two algorithms: one described by Bond et al (1999) and later specified by Ogren (2010), which is hereafter referred to as B1999, and the other determined by Virkkula et al (2005) and later corrected by Virkkula (2010), which is hereafter referred to as V2010. The algorithms of Müller et al (2014) and Li et al (2020) were not applied. The B1999 correction algorithm revisited by Ogren et al (2010) is given by…”

“…According to an IPCC report (IPPC, 2013), one of the greatest uncertainties in determining the global radiative forcing is related to atmospheric aerosol particles. Reasons for the large uncertainty are the complex nature of aerosolcloud interactions and also the great spatiotemporal variation of the particles (Lohmann and Feichter, 2005). Since the number concentration, size distribution, chemical composition, and shape of the particles vary in both space and time, it is challenging to model and estimate the effect that the aerosol particles have on climate on a global scale (IPPC, 2013).…”

“…Therefore, the instruments report a lower σ abs for loaded filters compared to pristine filter measurements. Several studies have developed algorithms to overcome this problem that has been observed with different instruments (Arnott et al, 2005;Bond et al, 1999;Collaud Coen et al, 2010;Li et al, 2020;Müller et al, 2014;Ogren, 2010;Schmid et al, 2006;Weingartner et al, 2003;Virkkula et al, 2005Virkkula et al, , 2007Virkkula, 2010). In general, after correcting the data for the multiple-scattering and loading effects, the absorption instruments agree rather well with the reference measurements (Drinovec et al, 2015;Hyvärinen et al, 2013;Park et al, 2010;Segura et al, 2014).…”

Correcting for filter-based aerosol light absorption biases at ARM’s SGP site using Photoacoustic data and Machine Learning

“…Various correction algorithms (Bond et al, 1999;Virkkula et al, 2005;Li et al, 2020) based on a general analytical equation form, have been developed and used in climate research facilities across the world. The general form of the various previously developed correction algorithms for PSAP is summarised in Eqn.…”

A comparison of three optical absorption photometers at a boreal forest site – effects of different correction algorithms

“…Therefore, the instruments report a lower σabs for loaded filters compared to pristine filter measurements. Several studies have developed algorithms and determined coefficients to overcome this problem observed with different instruments (Arnott et al, 2005;Bond et al, 1999;Collaud Coen et al, 2010;Li et al, 2020;Müller et al, 2014;Ogren, 2010;Schmid et al, 2006;Weingartner et al, 2003;Virkkula et al, 2005;Virkkula et al, 2007;Virkkula, 2010). The outcome of the different algorithms, however, varies and they may affect for example the wavelength dependency of the σabs.…”