Spatial distribution of aerosol microphysical and optical properties and direct radiative effect from the China Aerosol Remote Sensing Network

Huizheng Che,Ke Gui,Yaqiang Wang,Leiku Yang,Emilio Cuevas-Agulló,Wei Gong,Philippe Goloub,Bing Qi,Yu Zheng,Renjian Zhang,Xiaochun Zhang,Hong Wang,Jing Chen,Xiangao Xia,Jun Zhu,Xiaoye Zhang,Huiling Zhao ,V Estellés ,Оleg Dubovik ,B N Holben ,Haiguang Yang

doi:10.5194/acp-19-11843-2019

Abstract

Abstract. Multi-year observations of aerosol microphysical and optical properties, obtained through ground-based remote sensing at 50 China Aerosol Remote Sensing Network (CARSNET) sites, were used to characterize the aerosol climatology for representative remote, rural, and urban areas over China to assess effects on climate. The annual mean effective radii for total particles (ReffT) decreased from north to south and from rural to urban sites, and high total particle volumes were found at the urban sites. The aerosol optical depth at 440 nm (AOD440 nm) increased from remote and rural sites (0.12) to urban sites (0.79), and the extinction Ångström exponent (EAE440–870 nm) increased from 0.71 at the arid and semi-arid sites to 1.15 at the urban sites, presumably due to anthropogenic emissions. Single-scattering albedo (SSA440 nm) ranged from 0.88 to 0.92, indicating slightly to strongly absorbing aerosols. Absorption AOD440 nm values were 0.01 at the remote sites versus 0.07 at the urban sites. The average direct aerosol radiative effect (DARE) at the bottom of atmosphere increased from the sites in the remote areas (−24.40 W m−2) to the urban areas (−103.28 W m−2), indicating increased cooling at the latter. The DARE for the top of the atmosphere increased from −4.79 W m−2 at the remote sites to −30.05 W m−2 at the urban sites, indicating overall cooling effects for the Earth–atmosphere system. A classification method based on SSA440 nm, fine-mode fraction (FMF), and EAE440–870 nm showed that coarse-mode particles (mainly dust) were dominant at the rural sites near the northwestern deserts, while light-absorbing, fine-mode particles were important at most urban sites. This study will be important for understanding aerosol climate effects and regional environmental pollution, and the results will provide useful information for satellite validation and the improvement of climate modelling.

Highlights

Atmospheric aerosols have important direct effects on climate because they can scatter and absorb radiant energy and, in so doing, affect the Earth’s energy balance (Charlson et al, 1992; Yang et al, 2016)
The volume concentration of total particles was found to be substantially higher at the urban sites
The volume of the coarse-mode particles was considerably larger than that of the fine-mode particles at the remote, arid, and semi-arid sites and at those sites on the Chinese Loess Plateau (CLP) or nearby, indicating that those areas were most strongly affected by larger particles, most likely mineral dust, as discussed below

Summary

Introduction

Atmospheric aerosols have important direct effects on climate because they can scatter and absorb radiant energy and, in so doing, affect the Earth’s energy balance (Charlson et al, 1992; Yang et al, 2016). The optical properties of the aerosol determine the particles’ direct effects on the Earth’s radiative balance and weather–climate change (Ramanathan et al, 2001; Eck et al, 2005; Myhre, 2009; Zhao et al, 2018; Che et al, 2019a; Li et al, 2016). Aerosol optical properties have been used in comprehensive studies of aerosol physical characteristics and chemical composition in many regions of China (Che et al, 2009c, 2018; Zhao et al, 2018)

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Conclusion