Abstract. The largest uncertainty in the estimation of climate forcing stems from atmospheric aerosols. In early spring and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi (Haze in China) project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP). Aerosol optical properties, including the scattering coefficient (σ sp ), the hemispheric back scattering coefficient (σ bsp ), the absorption coefficient (σ ap ), as well as the single scattering albedo (ω), are presented. The diurnal and seasonal variations are analyzed together with meteorology and satellite data. The mean values of σ sp, 550nm of the dry aerosol in spring and summer are 280±253 and 379±251 Mm −1 , respectively. The average σ ap for the two periods is respectively 47±38 and 43±27 Mm −1 . The mean values of ω at the wavelength of 637 nm are 0.82±0.05 and 0.86±0.05 for spring and summer, respectively. The relative high levels of σ sp and σ bsp are representative of the regional aerosol pollution in the NCP. Pronounced diurnal cycle of σ sp , σ ap and ω are found, mainly influenced by the evolution of boundary layer and the accumulation of local emissions during nighttime. The pollutants transported from the southwest of the NCP are more significant than that from the two megacities, Beijing and Tianjin, in both spring and summer. An optical closure experiment is conducted to better under-

Abstract. Aerosol pollution in eastern China is an unfortunate consequence of the region's rapid economic and industrial growth. Here, sun photometer measurements from seven sites in the Yangtze River Delta (YRD) from 2011 to 2015 were used to characterize the climatology of aerosol microphysical and optical properties, calculate direct aerosol radiative forcing (DARF) and classify the aerosols based on size and absorption. Bimodal size distributions were found throughout the year, but larger volumes and effective radii of fine-mode particles occurred in June and September due to hygroscopic growth and/or cloud processing. Increases in the fine-mode particles in June and September caused AOD 440 nm > 1.00 at most sites, and annual mean AOD 440 nm values of 0.71-0.76 were found at the urban sites and 0.68 at the rural site. Unlike northern China, the AOD 440 nm was lower in July and August (∼ 0.40-0.60) than in January and February (0.71-0.89) due to particle dispersion associated with subtropical anticyclones in summer. Low volumes and large bandwidths of both fine-mode and coarsemode aerosol size distributions occurred in July and August because of biomass burning. Single-scattering albedos at 440 nm (SSA 440 nm ) from 0.91 to 0.94 indicated particles with relatively strong to moderate absorption. Strongly absorbing particles from biomass burning with a significant SSA wavelength dependence were found in July and August at most sites, while coarse particles in March to May were Published by Copernicus Publications on behalf of the European Geosciences Union. 406H. Che et al.: Aerosol optical properties and direct radiative forcing mineral dust. Absorbing aerosols were distributed more or less homogeneously throughout the region with absorption aerosol optical depths at 440 nm ∼ 0.04-0.06, but inter-site differences in the absorption Angström exponent indicate a degree of spatial heterogeneity in particle composition. The annual mean DARF was −93 ± 44 to −79 ± 39 W m −2 at the Earth's surface and ∼ −40 W m −2 at the top of the atmosphere (for the solar zenith angle range of 50 to 80 • ) under cloud-free conditions. The fine mode composed a major contribution of the absorbing particles in the classification scheme based on SSA, fine-mode fraction and extinction Angström exponent. This study contributes to our understanding of aerosols and regional climate/air quality, and the results will be useful for validating satellite retrievals and for improving climate models and remote sensing algorithms.

Abstract. Long-term measurements of aerosol optical depths (AOD) and Angstrom exponents (Alpha) made for CARSNET were compiled into a climatology of aerosol optical properties for China. Quality-assured monthly mean AODs are presented for 50 sites representing remote, rural, and urban areas. AODs were 0.14, 0.34, 0.42, 0.54, and 0.74 at remote stations, rural/desert regions, the Loess Plateau, central and eastern China, and urban sites, respectively, and the corresponding Alpha values were 0.97, 0.55, 0.82, 1.19, and 1.05. AODs increased from north to south, with low values (< 0.20) over the Tibetan Plateau and northwestern China and high AODs (> 0.60) in central and eastern China where industrial emissions and anthropogenic activities were likely sources. AODs were 0.20–0.40 in semi-arid and arid regions and some background areas in north and northeast China. Alphas were > 1.20 over the southern reaches of the Yangtze River and at clean sites in northeastern China. In the northwestern deserts and industrial parts of northeast China, Alphas were lower (< 0.80) compared with central and eastern regions. Dust events in spring, hygroscopic particle growth during summer, and biomass burning contribute the high AODs, especially in northern and eastern China. The AODs show decreasing trends from 2006 to 2009 but increased ~ 0.03 yr−1 from 2009 to 2013.

This is the first study to examine MVPA and ST among different disability types at school using accelerometry. Given the low levels of PA, this population should receive priority in the development of cost-effective interventions to improve their PA opportunities.

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The largest uncertainty in the estimation of radiative forcings on climate stems from atmospheric aerosols. In winter and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP). Aerosol optical properties including scattering coefficient (&sigma;_sp), hemispheric back scattering coefficient (&sigma;_bsp), absorption coefficient (&sigma;_ap, as well as single scattering albedo (&omega;) are presented. The characteristics of diurnal and seasonal variations are analyzed together with the meteorological and satellite data. The mean values of &sigma;_{sp, 550 nm} of the dry aerosol in winter and summer are 280 &plusmn; 253 and 379 &plusmn; 251 Mm⁻¹, respectively. The average &sigma;_ap for the two periods are respectively 47 &plusmn; 38 and 43 &plusmn; 27 Mm⁻¹. The mean values of &omega; are 0.83 &plusmn; 0.05 and 0.87 &plusmn; 0.05 for winter and summer, respectively. The relative high levels of &sigma;_sp and &sigma;_bsp are representative of the regional polluted aerosol of the North China Plain. Pronounced diurnal cycle of &sigma;_sp, &sigma;_ap and &omega; are found, mainly influenced by the evolution of boundary layer and accumulation of local emissions during night-time. Regional transport of pollutants from southwest in the NCP is significant both in winter and summer, while high values of &sigma;_sp and &sigma;_ap correlate with calm winds in winter, which indicating the significant contribution of local emissions. An optical closure experiment is conducted to better understand uncertainties of the measurements. Good correlations (<i>R</i>>0.98) are found between values measured by nephelometer and values calculated with a modified Mie model. Monte Carlo simulations show an uncertainty of about 30% for the calculations. Considering all possible uncertainties of measurements, calculated &sigma;_sp and &sigma;_bsp agree well with measured values, indicating a stable performance of instruments and thus a reliable aerosol optical data

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