六盘山区云凝结核分布特征及其气象影响因子

Characteristics of Cloud Condensation Nuclei Distribution in Liupan Mountains and Its Meteorological Influences

摘要:

利用六盘山地区2022年9月至2023年8月期间6个过饱和度（0.1%、0.2%、0.3%、0.4%、0.6%、0.8%）下云凝结核（Cloud Condensation Nuclei，CCN）观测资料和气象数据，研究六盘山CCN变化特征及其影响因子。结果表明：①受气象因素、污染源和过饱和度等的影响,六盘山区CCN平均浓度为589 cm^-3。各过饱和度下的CCN粒子数量分布呈单峰型，随过饱和度的增大，粒子数量峰值粒径增大，0.8%过饱和度下的峰值粒径为3.5～4.0 μm。CCN数浓度（N_CCN）月变化为6月最高，2月最低；日变化表现为下午和晚上浓度增加。②冬半年降雪量<2.5 mm、夏半年降雨量<0.5 mm时N_CCN浓度较高；非降水天气下相对湿度在30%～90%、风速<15 m/s、冬半年为偏东风、夏半年风向为135°～180°时N_CCN较高。冬半年非降雪天气CCN平均数浓度谱高于降雪天气、夏半年降雨和非降雨天气。③雨强为1.1 mm/h和6.7 mm/h，N_CCN减少率分别为10.16 cm^-3·h^-1和20.11 cm^-3·h^-1；拟合CCN活化谱发现，CCN活化谱参数C值大多时期明显较大（大于1000），拟合系数k值较高（约0.7以上），表明该地区常具有明显的大陆性特征。

Abstract:

Using the observation data of cloud condensation nuclei (CCN) under 0.1%, 0.2%, 0.3%, 04%, 0.6%, and 0.8% supersaturations and meteorological data in the Liupan Mountain area from September 2022 to August 2023, this study explores the variation characteristics of CCN in Liupan Mountain and their influencing factors. The results show that, affected by meteorological factors, pollution sources, supersaturation, etc.: (1) The average concentration of CCN in the Liupan Mountain area is 589 cm^-3. The number distribution of CCN particles under each supersaturation shows a unimodal pattern. With the increase in supersaturation, the peak particle size of the number of particles increases, and the peak particle size under 0.8% supersaturation is 3.5 to 4.0 μm. The monthly variation of CCN number concentration shows the highest in June and the lowest in February; the diurnal variation shows that the concentration increases in the afternoon and evening. (2) The CCN number concentration is relatively high when the snowfall in the winter half-year is less than 2.5 mm and the rainfall in the summer half-year is less than 0.5 mm; in non-precipitation weather, the CCN number concentration is relatively high when the relative humidity is 30% to 90%, the wind speed is less than 15 m/s, the wind direction is easterly in the winter half-year, and the wind direction is 135° to 180° in the summer half-year. The CCN number concentration mean spectrum in non-snowfall weather in the winter half-year is higher than that in snowfall weather and the summer half-year. (3) When the rain intensity is 1.1 mm·h^-1 and 6.7 mm/h, the CCN number concentration reduction rates are 10.16 cm^-3·h^-1 and 20.11 cm^-3·h^-1, respectively; by fitting the CCN activation spectra, it is found that the parameter C of the CCN activation spectrum is significantly large in most periods (greater than 1000), and the fitting coefficient k is high (about 0.7 or more), indicating that the area often has obvious continental characteristics.