Influence of aerosol physicochemical properties on CCN activation during the Asian winter monsoon at the summit of Mt. Lu, China

Abstract

To better understand the characteristics of high-altitude aerosol (or condensation nuclei, CN) and cloud condensation nuclei (CCN) in East China during the Asian winter monsoon, a field campaign focused on aerosol and CCN was set up in the area of Mt. Lu during the period from 5 November to 10 December 2019. The features of CCN and CCN formation at Mt. Lu were analyzed. The CCN spectra at Mt. Lu belongs to a polluted continental type, which could be parameterized using N = 2498S0.31, with S denoting supersaturation. The average and standard deviation of the CCN (S = 0.4%) and CN concentrations were 1936 ± 1007 cm−3 and 3041 ± 1646 cm−3, respectively. The CCN activation fraction (AF) values are 0.43, 0.57, 0.64, 0.69, and 0.72 at S = 0.2%, S = 0.4%, S = 0.6%, S = 0.8% and S = 1%, respectively. The aerosol composition would be more important than aerosol size in determining CCN activation at Mt. Lu. The CCN (CN) number concentration had a clear diurnal variation with maximal and minimal values at 13:00 (12:00 and 18:00) and 07:00 (07:00), respectively. Nearly 68.7% of the air mass reaching Mt. Lu came from the northern area. The higher-sulfate-ratio air mass has a relatively high AF efficiency.