Abstract. Size-resolved and bulk activation properties of aerosols were measured at a regional/suburban site in the North China Plain (NCP), which is occasionally heavily polluted by anthropogenic aerosol particles and gases. A Cloud Condensation Nuclei (CCN) closure study is conducted with bulk CCN number concentration (N CCN ) and calculated CCN number concentration based on the aerosol number size distribution and size-resolved activation properties.The observed CCN number concentration (N CCN-obs ) are higher than those observed in other locations than China, with average N CCN-obs of roughly 2000, 3000, 6000, 10 000 and 13 000 cm Size-resolved activation measurements show that most of the 300 nm particles are activated at the investigated supersaturations, while almost no particles of 30 nm are activated even at the highest supersaturation of 0.72%. The activation ratio increases with increasing supersaturation and particleCorrespondence to: C. S. Zhao (zcs@pku.edu.cn) size. The slopes of the activation curves for ambient aerosols are not as steep as those observed in calibrations with ammonium sulfate suggesting that the observed aerosols is an external mixture of more hygroscopic and hydrophobic particles.The calculated CCN number concentrations (N CCN-calc ) based on the size-resolved activation ratio and aerosol number size distribution correlate well with the N CCN-obs , and show an average overestimation of 19%. Sensitivity studies of the CCN closure show that the N CCN at each supersaturation is well predicted with the campaign average of sizeresolved activation curves. These results indicate that the aerosol number size distribution is critical in the prediction of possible CCN. The CCN number concentration can be reliably estimated using time-averaged, size-resolved activation efficiencies without accounting for the temporal variations.

No abstract

No abstract

No abstract

No abstract

Articles you may be interested inSome analytical results for thermal transpiration and the mechanocaloric effect in a cylindrical tube Measurements have been made of the pressure ratio, R, due to thermal transpiration in hydrogen, helium, argon, and nitrogen between a warm temperature of 297°K and cold temperatures of 77.3 or 195°K. It is found that R depends on X, the product of the pressure and tube diameter according to the empirical relation,where A and B are constants which depend on the gas and on the warm and cold temperatures, and Rm = (TdT2)!. The R against P 2, and therefore X, curves for different gases are found to be related by a "pressure shifting factor" f.The use of these results to correct measurements of adsorption equilibrium and vapor pressures at low pressures and low temperatures is discussed.Vapor pressures at 77.3°±0.5°K corrected for the thermo molecular pressure effect have been measured for krypton and xenon:Krypton Xenon l.754±0.OO2 mm; 1.93 ±O.01XlO-a mm.

No abstract

No abstract