L. Mcinnes et al., APPORTIONMENT OF LIGHT-SCATTERING AND HYGROSCOPIC GROWTH TO AEROSOL COMPOSITION, Geophysical research letters, 25(4), 1998, pp. 513-516
During a recent campaign at the NOAA CMDL monitoring station on Sable
Island, Canada (43.93 degrees N, 60.01 degrees W) a dual-nephelometer
humidigraph measured the hygroscopic growth factor of aerosol scatteri
ng, f(RH)(sigma(sp)), one of the key parameters necessary for estimati
ng short-wave aerosol radiative forcing. Measurements revealed less gr
owth anthropogenically influenced aerosols than for marine, f(RH)(sigm
a(sp)) of 1.7 +/- 0.1 vs. 2.7 +/- 0.4, where f(RH)(sigma(sp)) = sigma(
sp(85%))/sigma(sp(40%)). combined measurement-modeling approach was us
ed to estimate sigma(sp) and its RH-dependence, based on the measured
particle size distribution and composition. The model suggested that d
ifferences in the particle size distribution, assuming the same aeroso
l composition, could not explain the observed differences in f(RH)(sig
ma(sp)). We have confirmed with individual particle analysis, that aer
osol composition was indeed responsible for the difference in f(RH)(si
gma(sp)). As well, the scattering contribution of organic carbon for t
he influenced case is at least as much as sulfate aerosol.