Multiple scattering correction factor estimation for aethalometer aerosol absorption coefficient measurement

We estimate the multiple scattering correction factor (Cref), which is an empirical constant required to correct aerosol absorption coefficient (σap) measurements for the multiple scattering artifacts of aethalometer, using a multiplier derived from a linear regression method (CrefLRL). Estimated CrefLRL 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 CrefLRL values and those of a previous study (CrefW03) 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. CrefW03 varies by up to 121% with increasing aerosol absorption coefficient (σap) at 532 and 781 nm, whereas CrefLRL varies by only 36.8%. CrefW03 and CrefLRL determined during CAPMEX were applied to year-round aethalometer σap measurements (σapW03 and σapLRL, respectively) at Gosan (GSN), Lulin (LLN), and Alert (ALT) stations. σapW03 and σapLRL were compared to concurrent σap measurements from Continuous Light Absorption Photometer (CLAP; σapCLAP). At GSN, the bias difference and root mean square difference of σapW03 from σapCLAP are ˗23.1 and 25.8%; however, those of σapLRL from σapCLAP are ˗9.0 and 17.9%, respectively. LLN and ALT both exhibit a greater difference between σapW03 and σapCLAP than between σapLRL and σapCLAP. This suggests that CrefLRLcan be applied to year-round aethalometer measurements. Furthermore, σapLRL agrees better with σapCLAP than σapW03 in all three environments. Copyright © 2019 American Association for Aerosol Research