Impact of aerosol hygroscopic growth on the direct aerosol radiative effect in summer on North China Plain. (December 2016)

• Record Type: Journal Article
• Authors: Kuang, Y.; Zhao, C.S.; Tao, J.C.; Bian, Y.X.; Ma, N.
• Is Part Of: Atmospheric environment. Volume 147(2016)
• Page Start: 224
• Page End: 233
• Publication Date: 2016-12
• Subjects: Relative humidity profiles -- Aerosol optical depth -- Single scattering albedo -- Asymmetry factor -- Aerosol optical properties; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2016.10.013
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: In this paper, relative humidity (RH) profiles and their impacts on the vertical variations of aerosol optical properties and the direct aerosol radiative effect (DARE) have been investigated based on surface measurements from the Haze in China campaign and sounding data from the North China Plain. Among the profiles obtained from July to September in 2008, about half have RHs greater than 80% within the mixed layer. The vertical variations in the aerosol optical properties at ambient RH, including the extinction coefficient ( σ ext ), single scattering albedo (SSA) and asymmetry factor ( g ), are remarkably different from the variations in the dry aerosols and are highly dependent on the RH profiles. Increases of the aerosol optical depth and column-averaged SSA and g due to aerosol water uptake can reach up to 64%, 0.052 and 0.079, respectively. The fractional contribution to the instantaneous DARE at the top of the atmosphere due to aerosol hygroscopic growth reaches 60% in high RH profiles. DARE estimates can be significantly biased if the RH dependence of SSA or g is not considered. We suggest that if their vertical profiles or column-averaged values are absent, then the ambient values of SSA and g at the surface should be used rather than the values of SSA and g obtained from dry aerosols when estimating DAREs. Highlights: High frequency of high RH (>80%) profiles within the mixed layer during daytime. Aerosol optical properties highly depend on RH profiles due to aerosol water uptake. Aerosol hygroscopicity contributes to direct aerosol radiative effect significantly.