Abstract
The current understanding of columnar aerosol optical and microphysical properties of different regions and seasons in China is insufficient due to the lack of measurements. Aiming to improve descriptions of aerosol models over China, this paper presents a systematic aerosol characterization of different sites based on a newly developed remote sensing network for aerosol observation, the Sun-sky radiometer Observation NETwork (SONET). One year of ground-based solar and sky radiation measurements of four typical sites of SONET (Beijing–urban-industrial site, Zhangye—rural site, Minqin—desert site, Zhoushan–oceanic site) are used to retrieve aerosol properties using similar inversion algorithms with AErosol RObotic NETwork (AERONET), including aerosol optical depth, Ångström exponent, volume size distribution, complex refractive index, single scattering albedo, and percentage of spherical particles. The retrieved properties among sites and seasons are found to be different in terms of magnitude, spectral dependence, and partition of fine and coarse mode, which can be primarily explained by different aerosol composition and mixing states that closely relate to the local climate, the natural environment, and most importantly, the ubiquitous anthropogenic impacts. For example, large dust particles greatly contribute to the low fine mode fraction in both volume concentration and optical depth for the Minqin site through the entire year, while abundant small particles that mainly come from emission sources dominate the size distribution and light extinction of aerosol in the summer at the Beijing site. The results also show general agreements with other studies on the aerosol properties at each site, however, some unique features are still noticeable, especially at the desert site and oceanic site (e.g., the unusually strong aerosol absorptivity indicated by the large imaginary refractive index and low single scattering albedo at the Minqin and Zhoushan sites), which can be partly attributed to the existence of absorbing particles coming from anthropogenic sources.
Highlights
Atmospheric aerosol is one of the most important determining factors of direct radiative forcing and indirect effects on clouds [1]
This paper aims to utilize one-year, ground-based remote sensing measurements in a newly developed network based on CE318 [43], the Sun-sky radiometer Observation NETwork (SONET), to investigate the seasonal optical and microphysical properties of aerosol from four typical sites over China
We compare Aerosol optical depth (AOD) measurements of Zhangye site (ZY) with other studies and find that ZY has much larger aerosol loadings (0.15 at 675 nm) than other rural sites (0.04 at 673 nm), and these can be attributed to the high percentage of dust particles, considering ZY suffers from dust impacts
Summary
Atmospheric aerosol is one of the most important determining factors of direct radiative forcing and indirect effects on clouds [1]. The assessments of radiative forcing depend greatly on aerosol optical properties [2,3]. Direct radiative forcing from aerosol is primarily connected to aerosol concentration (aerosol optical depth, AOD), particle size, and absorption/scattering properties [4]. Aerosol optical properties such as AOD, single scattering albedo (SSA), and fine mode fraction in optical depth (FMF) are important since they are usually used to describe aerosol pollution events, as more and more significant atmospheric pollution caused by aerosols has caused serious health and traffic safety issues in recent years, especially in China [10,11]. Whether the assessments of aerosol radiative forcing and environmental effects are realistic and meaningful depends greatly on if the optical and microphysical properties of aerosol are well-grounded
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