Multiple scattering correction factor estimation for aethalometer aerosol absorption coefficient measurement

We estimate the multiple scattering correction factor (C_ref), which is an empirical constant required to correct aerosol absorption coefficient (σ_ap) measurements for the multiple scattering artifacts of aethalometer, using a multiplier derived from a linear regression method (C_ref^LRL). Estimated C_ref^LRL values during the Cheju ABC Plume Monsoon EXperiment (CAPMEX) are 3.99 (405 nm), 4.48 (532 nm), and 5.46 (781 nm) using aethalometer and 3-wavelength PhotoAcoustic Soot Spectrometer (PASS-3). The difference between these C_ref^LRL values and those of a previous study (C_ref^W03) are ˗8.0% (405 nm), 20.1% (532 nm), and 30.2% (781 nm); the difference is greater at larger wavelengths because the linear regression line intercept is larger. C_ref^W03) varies by up to 121% with increasing aerosol absorption coefficient (σ_ap) at 532 and 781 nm, whereas C_ref^LRL varies by only 36.8%. C_ref^W03 and C_ref^LRL determined during CAPMEX were applied to year-round aethalometer σ_ap measurements (σ_ap^W03 and σ_ap^LRL, respectively) at Gosan (GSN), Lulin (LLN), and Alert (ALT) stations. (σ_ap^W03) and σ_ap^LRL) were compared to concurrent σ_ap measurements from Continuous Light Absorption Photometer (CLAP; σ_ap^CLAP). At GSN, the bias difference and root mean square difference of σ_ap^W03 from σ_ap^CLAP are ˗23.1 and 25.8%; however, those of σ_ap^LRL from σ_ap^CLAP are ˗9.0 and 17.9%, respectively. LLN and ALT both exhibit a greater difference between σ_ap^W03 and σ_ap^CLAP than between σ_ap^LRL and σ_ap^CLAP. This suggests that C_ref^LRL can be applied to year-round aethalometer measurements. Furthermore, C_ref^LRL agrees better with σ_ap^CLAP than σ_ap^W03 in all three environments.