上海干霾与湿霾气溶胶消光特性的比较

Comparison of the extinction of aerosols and humidity influence between dry and damp haze periods in Shanghai

利用2009年3月？2010年2月上海市城市环境气象中心的微脉冲激光雷达资料，通过分析消光系数和光学厚度（AOD）等光学特性参量揭示了上海地区发生干霾和湿霾时气溶胶的垂直分布特征，并分析了相对湿度对干霾和湿霾的影响.结果表明：干霾日的发生频率要明显高于湿霾日；不同强度霾中，干霾在轻微霾与轻度霾中所占比例较多，而中度霾和重度霾中湿霾的比例增大，其中重度霾中湿霾多于干霾；湿霾时段的消光系数变化波动明显比干霾时段剧烈，干霾时消光在0.10 km^-1左右波动，而湿霾时消光从0.01～1.00 km^-1变化不等；在500 m以下的近地面大气，湿霾的消光基本大于干霾；干霾时段AOD无明显季节变化，而湿霾时段AOD变化趋势表现为春季〉冬季〉夏季〉秋季，且90%来自于低层大气（0～1 km）的贡献；夏季相对湿度较大，湿霾最多，但湿霾中重度霾所占比例是所有季节中最小的，轻微霾比例最大；而春、秋、冬三季发生湿霾时的能见度明显低于干霾时，说明湿度的增加对消光的贡献明显增大.

Using the observational data of micro-pulse lidar from Shanghai Urban Environmental Meteorological Center, the vertical distribution of aerosol extinctive properties during dry and damp haze periods in Shanghai were demonstrated by analyzing the extinction coe？cient and the optical depth （AOD）. The influence of humidity on dry and damp haze was also analyzed. Observation data results from one year showed that dry haze occurred significantly more frequently than damp haze;as for the different intensities of haze, the proportion of dry hazy days in the slight haze and mild haze was more than that in moderate and severe haze but the proportion of damp haze increased in moderate and severe haze, particularly there were more dry haze days in severe haze. Damp haze in the period of the extinction coeffcient change fluctuated significantly than dry haze time. Stem haze extinction occurred in the 0.1 km, with about fluctuations, and wet haze extinction that occurred at 0.01～1 km^-1 varied. In the 500 m atmosphere near the ground surface, wet haze of extinction was basically more severe than dry haze. During stem haze time there was no obvious seasonal changes in AOD while during wet haze time the changing trend of the AOD performance is spring〉autumn〉winter〉summer, and 90%was from the lower atmosphere （0～1 km）. In summer the particle concentration was the lowest, but wet haze occurred most frequently because of the bigger relative summer humidity,whereas when wet haze happened the visibility was obviously lower than the stem haze in spring, autumn and winter. This shows that the contribution of light cancelation had increased obviously because of the increase of humidity. In short, during the summer, particles were fewer, and their proportion was the least of the seasons according to the severe haze in wet haze and the slight haze proportion was the largest, and therefore the visibility was not very poor.