高污染下云凝结核对雨、雾滴谱的影响

Impacts of CCN on droplet spectra of rain and fog during high pollution days

利用气候基准站、云凝结核计数器、雾滴谱仪和雨滴谱仪等观测资料,分析威宁污染时期云凝结核(CCN)对雨雾滴谱的影响.结果表明:观测期间威宁CCN数浓度很高,S=0.2%、0.4%、0.6%和0.8%时的平均CCN浓度分别为2884、8003、10470、11685cm^(-3),与部分重污染城市相当;CCN有明显的日变化特征,分别在12:00、16:00和20:00出现峰值,与居民生活排放、火电源排放、湍流交换和气象条件等有关;利用N=CS^k式拟合威宁CCN活化谱,平均拟合参数C=14288cm^(-3),k=0.8,表明该地属典型大陆型核谱;威宁冬季云层薄、云顶低的云系特点提供了宏观天气背景,高浓度CCN是导致此次雨、雾过程弱,滴谱窄的重要微观条件.

Based on observational data obtained by a cloud condensation nuclei (CCN) counter, a fog droplet spectrometerand an raindrop disdrometer, together with ground-based meteorological data, the impacts of atmospheric pollutants onCCN and the droplet spectra of rain and fog were analyzed. Results showed that: the CCN concentration in Weiningremained very high during the observation period, and the average CCN number concentration were 2884, 8003, 10470and 11685cm-3at S = 0.2%, 0.4%, 0.6% and 0.8%, respectively, which were comparable with those obtained in pollutedcities; the CCN concentration displayed a significant daily variation, peaking at 12:00, 16:00 and 20:00, respectively,which was relate to human activities, power plants emissions, turbulent exchange and meteorological conditions; the CCNspectra can be fitted by the expression N = CSk, with the fitting parameter C = 14288cm-3 and k = 0.8, indicating that theCCN spectra can be classified as a typical continental type. The precipitation characteristics of the stratiform cloud inWeining provided macro synoptic situations, and high CCN concentrations were an important microphysical condition fornarrow droplet spectra of rain and fog.