Multiple scattering correction factor estimation for aethalometer aerosol absorption coefficient measurement

摘要

We estimate the multiple scattering correction factor (C-ref), which is an empirical constant required to correct aerosol absorption coefficient (sigma(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 (rap) at 532 and 781nm, 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 rap measurements (sigma(W03)(ap) and sigma(LRL)(ap), respectively) at Gosan (GSN), Lulin (LLN), and Alert (ALT) stations. sigma(W03)(ap) and sigma(LRL)(ap) were compared to concurrent rap measurements from Continuous Light Absorption Photometer (CLAP; sigma(ap)(CLAP)). At GSN, the bias difference and root mean square difference of sigma(W03)(ap) from sigma(ap)(CLAP) are. 23.1 and 25.8%; however, those of sigma(LRL)(ap) from sigma(ap)(CLAP) are. 9.0 and 17.9%, respectively. LLN and ALT both exhibit a greater difference between sigma(W03)(ap) and sigma(ap)(CLAP) than between sigma(LRL)(ap) and sigma(ap)(CLAP). This suggests that C-ref(LRL) can be applied to year-round aethalometer measurements. Furthermore, sigma(LRL)(ap) agrees better with sigma(ap)(CLAP) than sigma(W03)(ap) in all three environments.