高层卷云对天气和气候有着重要的影响,其消光后向散射比是它的一个重要光学特性。假设卷云上方和下方没 有气溶胶,只有大气分子,由激光雷达信号就可反演出卷云的透过率和光学厚度,进而算出卷云的消光后向散射比。 对美国汉普顿大学的532 nm通道激光雷达测量的卷云数据进行了分析,数据采集期间从2007年1月至10月,共选取 了光学厚度在0.081.5之间的798组卷云数据。计算结果表明:卷云高度主要分布在7 13.5 km之间;卷 云消光后向散射比平均值为21.4 sr,月季特征并不很明显,概率分布呈现出正态分布特征;光学厚度的概率分 布函数说明大部分为薄卷云。

High cirrus clouds have large influence on weather and climate, and its lidar ratio is an important optical property. Suppose that there is only molecules without aerosol above and below the clouds, the transmittance and optical thickness of clouds can be retrieved from lidar data, and the lidar ratio of clouds. Analysis was performed on the clouds data acquired from 532nm lidar of Hampton University. Observation was performed from January to October 2007. 798 samples with optical thickness between 0.08 and 1.5 were selected. Results show that cirrus clouds observed are mostly in 7~13.5 km altitudes. The lidar ratio is 21.4sr in average, the change of the lidar ratio with season is not obvious, the probability distribution function of lidar ratio appears normal distribution feature. The probability distribution function of optical thickness indicates that most clouds are thin clouds.