南京不同天气和能见度下云凝结核的观测分析

Observational study of cloud condensation nuclei under different weather and visibility in Nanjing

利用美国DMT公司生产的云凝结核(Cloud Condensation Nuclei,CCN)计数器(DMTCCNC),对2013年4—12月南京地区CCN进行观测。对不同天气条件下CCN活化谱拟合,霾天C值最高,为13 085 cm-3,雨后C值降至8 054 cm-3,属于大陆性核谱。不同能见度条件下CCN活化谱特征有明显差异,南京地区不同程度霾天CCN数浓度均远高于轻雾天,浓雾时期CCN数浓度显著偏高。CCN数浓度受到气象要素和天气状况、气溶胶源排放等因素影响。南京地区气溶胶凝结核(Condensation Nuclei,CN)数浓度和CCN数浓度的拟合结果显示出较好的相关性。CCN数浓度值:冬季>春季>秋季>夏季,春季CCN数浓度日变化有三峰趋势,夏季基本呈单峰型,秋季、冬季双峰特征突出。气溶胶源排放、环境气象条件和气溶胶理化特性均会影响CCN数浓度的季节变化。

A Droplet Measurement Technologies （DMT） Cloud Condensation Nuclei Counter （CC- NC） was used to observe the number concentration of Cloud Condensation Nuclei （CCN） under different weather and visibility in Nanjing from April to December, 2013. The fitted CCN spectra for various weather conditions are obtained by using the expression N= CS^k, in which C reaches the highest 13 085 -3 cm on haze days ,but fall to 8 054 cm^-3 after rain, and all of them exhibit a continental type. Character- istics of CCN activation spectra under different visibility conditions are different obviously. CCN number concentration is apparently higher in all kinds of haze processes than in light fog process, and becomes rather high in a heavy fog process. CCN number concentration is affected by meteorological elements, weather condition and aerosol source emission. Based on the observations,a relationship between the CCN number concentration and aerosol number concentration is established and shows good correlation. CCN number concentration： winter〉spring〉autumn〉summer. There is a three-peak tendency of diurnal variation in spring, a unimodal type in summer and an distinctive bimodal characteristic in autumn and winter. Seasonal changes of CCN number concentration is affected by aerosol source emission, environmental meteorological condition, physical and chemical properties of aerosol.