Measurement of cloud condensation nuclei (CCN) and CCN closure at Mt. Huang based on hygroscopic growth factors and aerosol number-size distribution

Abstract

The number of cloud condensation nuclei (CCN) may indirectly influence the radiative balance of the atmosphere by changing the number of cloud droplets, which in turn changes the albedo, longevity and precipitation intensity of clouds. The spatial and temporal distribution of the CCN concentrations and the influence of particles on CCN activation spectra have received much attention. Measurements of CCN concentrations, aerosol number-size distribution and hygroscopic growth factors were conducted during the periods June 30 to July 17 and July 24 to 28, 2014, at the peak of Mt. Huang (1840 m above sea level). The results show that the CCN concentration were 419 ± 414 cm−3, 806 ± 720 cm−3, 1292 ± 905 cm−3, 1380 ± 873 cm−3, and 1506 ± 867 cm−3 at supersaturation levels of 0.1%, 0.2%, 0.5%, 0.7%, and 1%, respectively. The equation Nccn = N0(1-exp(-BSk)) fits the average CCN spectrum over the observation period. The CCN concentrations were calculated from the hygroscopic growth factors and the aerosol number-size distribution. The calculated CCN concentrations and measured CCN concentrations show close correlation and high accuracy. An analysis of the variation in the particle number-size distribution and hygroscopic growth factors indicates that the change in particle number-size distribution is the primary factor affecting the CCN concentrations.