Observational Study of Cloud Condensation Nuclei Properties at Various Altitudes of Huangshan Mountains

To investigate the vertical variability of cloud condensation nuclei (CCN) along mountain peaks in alpine regions of eastern China, the number concentration of CCN were obtained using a cloud condensation nuclei counter (CCNC) at three altitudes of Huangshan Mountains in June 2011. The results show that the time series of CCN concentration at these altitudes were nearly consistent and that the CCN concentration decreased with altitude. At a supersaturation level of 0.8%, the average CCN number concentrations were 1105.62 cm^-3, 1218.39 cm^-3, and 1777.78 cm^-3 at the foot, mid-height and summit of the mountain, respectively. The occurrence frequency of a high CCN concentration of more than 1000 cm^-3 recorded at the foot of the mountain is higher than that recorded at mid-height and the summit of the mountain. These results suggest that the environment at the foot of the mountain was influenced by the pollution sources in the surrounding areas which were heavier than those at mid-height and the summit. A bimodal pattern at both the summit and the foot of the mountain was presented in the diurnal variation. A peak appeared at forenoon and at afternoon, which is related to variation in the atmospheric boundary layer height and the valley wind. The fitted CCN spectra for various weather conditions at the summit of the mountain were obtained using the expressionN= CS^k, and the properties were analyzed. The results show that the fitted spectra parameter C was 2798, 384, and 765 on sunny, rainy, and foggy days, respectively, which is lower than the results recorded in some polluted cities. The size distribution of the CCN is shown to be a clean continental type. The results of this study will be conducive to a better understanding of the temporal and spatial distributions of CCN, particularly for eastern China. In addition, the basis for observation and parameterization schemes will be improved for the presentation of cloud activation in numerical models over this region.