A comparative study of cloud condensation nuclei measured between non-heating and heating periods at a suburb site of Qingdao in the North China

In this paper, we studied concentrations of cloud condensation nuclei (CCN) and CCN activity measured at a suburb site of Qingdao in the North China during a non-heating period from 19 May to 3 June 2013 and a heating period from 6 November to 6 December 2013. Concentrations of CCN during the non-heating period were 3.1 ± 1.9 (mean ± standard deviation), 4.9 ± 3.4, 5.6 ± 3.9, 6.1 ± 4.3 and 6.5 ± 4.6 in unit of ×103 cm−3 at supersaturation (SS) of 0.2%, 0.4%, 0.6%, 0.8% and 1.0%, respectively. The corresponding CCN activities of atmospheric particles were 0.28 ± 0.17, 0.43 ± 0.24, 0.48 ± 0.26, 0.52 ± 0.27 and 0.54 ± 0.28, respectively. Concentrations of CCN during the heating period were 3.1 ± 1.3, 6.4 ± 2.3, 8.5 ± 2.9, 9.6 ± 3.5 and 10 ± 3.9 in unit of ×103 cm−3 at SS of 0.2%, 0.4%, 0.6%, 0.8% and 1.0%, respectively. The corresponding CCN activities were 0.11 ± 0.06, 0.24 ± 0.11, 0.31 ± 0.14, 0.35 ± 0.15 and 0.37 ± 0.15, respectively. At SS ≥ 0.4%, concentrations of CCN were significantly larger during the heating period than during the non-heating period with 95% confidence because of larger particle number concentrations associated. However, CCN activities were significantly lower during the heating period than during the non-heating period at each SS. The lower CCN activities during the heating period were analyzed in terms of origins, median mobility diameter and possible chemical composition of atmospheric particles. However, when new particle formation events during the heating and the non-heating periods were considered alone, CCN activities of grown new particles at the same size range sometimes appeared to be constant regardless of the heating or non-heating periods.