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

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.

Reversal of Aerosol Properties in Eastern China with Rapid Decline of Anthropogenic Emissions

“…While there have been numerous aerosol remote sensing sites in China [7], few have continuous long-term observations. Despite only four AERONET sites being used, consistent trends of aerosol properties in these sites demonstrate the regional transition of particle pollution under the background of national air quality control measures.…”

“…As one of the largest pollution hotspots in the world, the huge anthropogenic emissions in eastern China have led to serious air pollution problems associated with obvious adverse effects [5,6]. The aerosol over China is characterized by heavy loading and intricate properties [7,8], which is further complicated by its interactions with Asian monsoon [9] and meteorological variables [10]. These aerosol particles can modify clouds' droplet size and lifetime [11], and thereby affects the frequency and intensity of regional precipitation [12].…”

Similarities and Differences in the Temporal Variability of PM2.5 and AOD Between Urban and Rural Stations in Beijing

“…The measurements are conducted on the south slope of a hill (293 m ASL) at SDZ that is surrounded by sparsely populated small villages. SDZ is one of the Chinese Aerosol Research Science Network (CARSNET) [19] stations that has regularly measured AOD by using a sun photometer since 2004. At UR, hourly PM 2.5 data measured by the beta-attenuation monitor (BAM) range from April 2008 to December 2018, and AERONET Version 3 cloud screened and quality assured level 2.0 data range from March 2004 to May 2018.…”

“…Diurnal variation of AOD based on 15 years worthy of AERONET observation data in the North China Plain (NCP) showed that AOD increased gradually from early morning to later afternoon [18]. Based on long-term observations of 50 China Aerosol Remote Sensing Network (CARSNET) sites, Che et al [19] found that annual mean AOD at 440 nm (AOD 440nm) increased from remote/rural sites (0.12) to urban sites (0.79).…”

A revisiting of the parametrization of downward longwave radiation in summer over the Tibetan Plateau based on high-temporal-resolution measurements

“…Wang and Liang (2009) evaluated clear-sky DLR parametrizations of Brunt (1932) and Brutsaert (1975) at 36 globally distributed sites, in which DLR data at two TP stations were used. Yang et al (2012) used hourly DLR data at six stations to study major characteristics of DLR and to assess the allsky parametrization of Crawford and Duchon (1998). Zhu et al (2017) evaluated 13 clear-sky and 10 all-sky DLR models based on hourly DLR measurements at five automatic meteorological stations.…”