Characteristics Of Atmospheric Ice Nuclei And Relationship With Aerosols In Nanjing

The Ice Nuclei (IN) were observed in Nanjing from May to December2011using a5L mixing cloud chamber and a static diffusion cloud chamber. The characteristics of IN concentration and the relationship between IN and aerosol were investigated by using the data of IN, aerosol, meteorological parameters and back trajectory data. The main research contents and conclusions are as follows:The mean concentration of total ice nuclei (all ice nucleation mechanisms) measured by the5L mixing cloud chamber was20.11L-1, the concentration of IN (the deposition nucleation or/and condensation freezing nucleation or/and contact freezing nucleation) under high water vapor conditions (5%calculated supersaturation with respect to water) and low water vapor conditions (5%calculated supersaturation with respect to ice) measured by the static diffusion cloud chamber was0.928L-1and0.291L-1, respectively. The large degree difference of results in IN measurements depended on several factors:the ice nucleation mechanisms that paricles were activated in different ways, the nucleation conditions in two chambers were different, and the error and accuracy of two instruments were not the same. The concentrations of IN in Nanjing area were less than that in Beijing, Qinghai and Shenyang which observed in recent years.IN which activate at different temperatures had consistently daily concentration variation characteristics. The IN under favorite conditions had a diurnal variation. The daytime concentration of IN was larger than that at night and peaked in the afternoon, which indicated that atmospheric IN is significantly influenced by turbulence intensity, the strong turbulence can entrainment dust from ground into atmosphere which could become IN. On the other hand, IN maybe have a correlation with human activities, and industrial pollution. The scavenging effect of precipitation on IN was obvious. The concentration of IN increased during the typhoon system, this may be associated with the blowing dust due to the strong wind. The IN levels in the Nanjing area increased with decreasing temperatures and increasing humidity. A case analysis focused on the relationship between IN and PM1(the particulate matter with diameter less than or equal to1μm) produced by biomass burning suggested that the product of the combustion may contribute to IN.The mean concentration of IN was0.352L-1at activation temperature(Ta) of-20℃and the supersaturation with respect to water (Sw) equals1%, the ratio of IN to aerosol concentrations in the size range of0.01-10μm was4×10-8. A comparison of IN in different air masses showed that the concentration of IN and aerosol in an air mass that originated from a polluted area to the east was the highest, but the ratio of IN to aerosols was the highest when the air mass originated to the northwest area, which might be because of the high ice-nucleating ability of dust particles.The correlation coefficient between IN and aerosol in different size ranges showed that IN with larger particle surface concentrations was much higher more highly correlated with aerosols. The ice nuclei empirical equation considering Ta and the aerosol number concentration (No.s～10μm) was obtained in this paper.