An overview of Sun–Sky Radiometer Observation Network (SONET) measurements in China is presented. Based on observations at 16 distributed SONET sites in China, atmospheric aerosol parameters are acquired via standardization processes of operational measurement, maintenance, calibration, inversion, and quality control implemented since 2010. A climatology study is performed focusing on total columnar atmospheric aerosol characteristics, including optical (aerosol optical depth, ÅngstrÖm exponent, fine-mode fraction, single-scattering albedo), physical (volume particle size distribution), chemical composition (black carbon; brown carbon; fine-mode scattering component, coarse-mode component; and aerosol water), and radiative properties (aerosol radiative forcing and efficiency). Data analyses show that aerosol optical depth is low in the west but high in the east of China. Aerosol composition also shows significant spatial and temporal variations, leading to noticeable diversities in optical and physical property patterns. In west and north China, aerosols are generally affected by dust particles, while monsoon climate and human activities impose remarkable influences on aerosols in east and south China. Aerosols in China exhibit strong light-scattering capability and result in significant radiative cooling effects.

No abstract

Abstract. The detailed formation mechanism of an increased number of haze events in China is still not very clear. Here, we found that reduced surface visibility from 1980 to 2010 and an increase in satellite-derived columnar concentrations of inorganic precursors from 2002 to 2012 are connected with each other. Typically, higher inorganic mass fractions lead to increased aerosol water uptake and light-scattering ability in elevated relative humidity. Satellite observation of aerosol precursors of NO2 and SO2 showed increased concentrations during the study period. Our in situ measurement of aerosol chemical composition in Beijing also confirmed increased contribution of inorganic aerosol fraction as a function of the increased particle pollution level. Our investigations demonstrate that the increased inorganic fraction in the aerosol particles is a key component in the frequently occurring haze days during the study period, and particularly the reduction of nitrate, sulfate and their precursor gases would contribute towards better visibility in China.

No abstract

This is the first investigation of the generalized linear regressions of PM 2.5 and aerosol optical depth (AOD) with the Campaign on atmospheric Aerosol Research-China network over the large high-concentration aerosol region during the period from 2012 to 2013. The map of the PM 2.5 and AOD levels showed large spatial differences in the aerosol concentrations and aerosol optical properties over China. The ranges of the annual mean PM 2.5 and AOD were 10-117 μg/m 3 and 0.12-1.11 from the clean regions to seriously polluted regions, from the almost "arctic" and the Tibetan Plateau to tropical environments. There were significant spatial agreements and correlations between the PM 2.5 and AOD. However, the linear regression functions (PM 2.5 = A*AOD + B) exhibited large differences in different regions and seasons. The slopes (A) were from 13 to 90, the intercepts (B) were from 0.8 to 33.3, and the correlation coefficients (R 2 ) ranged from 0.06 to 0.75. The slopes (A) were much higher in the north (41-99) than in the south (13-64) because the extinction efficiency of hygroscopic aerosol was rapidly increasing with the increasing humidity from the dry north to the humid south. Meanwhile, the intercepts (B) were generally lower, and the correlation coefficients (R 2 ) were much higher in the dry north than in the humid south. There was high consistency of AOD versus PM 2.5 for all sites in three ranges of the atmospheric column precipitable water vapor (PWV). The segmented linear regression functions were y = 84.66x + 9.85 (PWV < 1.0), y = 69.47x + 11.87 (1.0 < PWV < 2.5), and y = 52.37x + 8.59 (PWV > 2.5). The correlation coefficients (R 2 ) were high from 0.64 to 0.70 across China. Key Points:• This is the first investigation of the relationship between PM2.5 and AOD with a network in China • The map of the PM2.5 and AOD levels showed large spatial differences over China • The segmented linear regression functions applied across China in three PWV rangesCorrespondence to:

No abstract

No abstract

Experiments have been carried out to study the effects of macroscopic pores on the damping behavior of foamed commercially pure aluminum (FA). The damping characterization was conducted on a multifunction internal friction apparatus (MFIFA). The FA specimens were prepared by an air pressure infiltration process. The size of the macroscopic pores was on the order of a millimeter and in large proportions, typically, up to 56 vol pct. The internal friction (IF) of the FA specimen was measured at low frequencies at room temperature. The measured IF shows that FA has a damping capacity, which is enhanced in comparison with bulk commercially pure aluminum, increases with increasing porosity, increases with decreasing macropore size, increases with increasing frequency, and increases with increasing strain amplitude. The microstructural analysis was performed using transmission electron microscopy (TEM). The TEM observations show that a moderate density of dislocation substructures exists near the grain boundaries in the FA. In order to explain these phenomena, the possible operative damping mechanisms in the FA are discussed in light of IF measurements and microstructural observations, and an approximate expression for IF is derived, which is based on the equation of plane waves in elastic material with voids.