AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Development of a Universal Correction Algorithm for Filter-Based Absorption Photometers
HANYANG LI, Gavin McMeeking, Andrew May, The Ohio State University
Abstract Number: 50 Working Group: Carbonaceous Aerosol
Abstract Light-absorbing atmospheric particles directly affect the Earth’s energy budget by absorbing solar radiation. There are various measurement approaches to quantify light absorption (Babs) in situ, but our interest here is filter-based absorption photometers due to their near-ubiquity in monitoring networks around the globe. One challenge with filter-based absorption photometers is that biases can arise due to the presence of the filter. Consequently, various correction algorithms exist to minimize these biases; some are applicable to the Particle Soot Absorption Photometer (PSAP), while others are applicable to the Aethalometer (AETH).
We conducted laboratory experiments to investigate aerosol emissions from simulated wildfires, including three filter-based absorption photometers: an AETH, a Continuous Light Absorption Photometer (CLAP) and a Tricolor Absorption Photometer (TAP). Our analysis of the Babs indicates that even when the correction algorithms are applied, issues remain such as: 1). Corrected filter-based Babs may remain biased relative to a reference value of Babs; 2). Derived products (such as absorption Ångström exponents) may differ based on the implemented correction algorithm; 3). The applicability of previous correction algorithms to more recently developed instruments (e.g., CLAP and TAP) remains ambiguous.
Consequently, we have developed a “universal” correction algorithm across multiple wavelengths that is applicable to any filter-based absorption photometer by combining observed filter-based Babs with scattering coefficient (e.g., from a co-located nephelometer) and reference Babs (e.g., from a co-located photoacoustic instrument). The algorithm can even extend to situations where a filter-based absorption photometer is operated without a co-located nephelometer. We have applied the algorithm to both laboratory data and ambient data (from the DOE ARM Southern Great Plains user facility). Our algorithm results in very good agreement between filter-based and in situ Babs for both source-generated biomass burning smoke and ambient aerosols.