Examination of parameterizations for CCN number concentrations based on in-situ aerosol activation property measurements in the North China Plain
1Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
2Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, China
3Shanghai Typhoon Institute, China Meteorological Administration, Shanghai, China
4Centre for Atmosphere Watch and Services, Chinese Academy of Meteorological Sciences, China Meteorological Administration, Beijing, China
Abstract. Precise quantification of cloud condensation nuclei (CCN) number concentrations is crucial for understanding aerosol indirect effect and characterizing this effect in models. An evaluation of various methods for CCN parameterization is carried out in this paper based on in-situ measurements of aerosol activation properties within HaChi (Haze in China) project. Comparisons are made by closure studies between methods using CCN spectra, bulk activation ratios, cut-off diameters and size-resolved activation ratios. The estimation of CCN number concentrations by the method using aerosol activation curves, either averaged over a day or with diurnal variation, is found to be most satisfying and straightforward. This could be well expected since size-resolved activation ratios include information regarding the effects of size-resolved chemical composition and mixing state on aerosol activation properties. The method using the averages of critical diameters, which are inferred from measured CCN number concentrations and particle number size distribution, also provides a good prediction of CCN number concentrations. Based on comparisons of all these methods in this paper, it is recommended that CCN number concentrations be predicted using particle number size distribution with inferred critical diameters or size-resolved activation ratios.