摘要
本文给出了CALIPSO卫星偏振激光雷达自2006年6月至2010年3月间探测的北京地区大气云层的统计特性,并根据理论研究结果对激光雷达探测的云进行了分类,当云的温度低于0℃时发现了过冷水的存在.统计结果表明:温度在0℃以上时,大气中的云大部分为水云;温度在0℃至-25℃之间时,大气中会有过冷水和水平导向的片状晶体的冰云存在;温度低于-45℃时,大气中的云则大部分由随机导向的晶体颗粒组成.最后,本文给出了水云、过冷水和卷云消偏振度、光学厚度和分布高度的季节特性:在夏季和春季时卷云的消偏振度及其高度值要比在冬季和秋季时的值高,并且卷云的高度受到平流层顶高度的调制;水云的消偏振度及高度值在夏季和春季时的值要比在秋季和冬季时的值高;在夏季和秋季时过冷水的高度达到最大值.结果表明:卷云的消偏振度值随着其高度的增加和温度的降低而相应地增加,然而过冷水的消偏振度值却随着其高度的增加而减少.
The statistical properties of clouds from June 2006 to March 2010 over Beijing derived from the CALIPSO lidar measurements are presented, and based on the theoretical analysis the detected clouds are classified. The super-cooled water clouds are found below the temperature of 0℃. From the statistical results, it appears that the clouds with cloud mid-layer temperature above 0℃ correspond primarily to the water clouds; the super-cooled water and horizontally oriented ice crystals are found to exist at the cloud mid-layer temperatures between 0℃ and --25℃ ; for cloud mid-layer temperature below --45℃, the observed clouds correspond primarily to the ice clouds with randomly oriented ice crystals. The annual averaged depolarization ratios, optical depth and altitude are reported for the water, super-cooled water and ice clouds, respectively. Moreover, the results indicate that the values of depolarization ratio and altitude of cirrus are generally higher in summer and spring than those in winter and autumn, and the cirrus altitude is modulated by the height of tropopause; while the values for the water clouds are generally higher in summer and spring than those in autumn and winter, and the altitudes of super-cooled water are high in summer and autumn. Additionally, the depolarization ratio of cirrus tends to linearly vary with the increase of altitude and the decrease of temperature, while the depolarization ratio of super-cooled water tends to decrease with the increase of its altitude.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2011年第10期2487-2494,共8页
Chinese Journal of Geophysics
基金
国家自然科学基金(40571097)
2010年北航博士创新基金资助
关键词
消偏振
激光雷达
弹性散射
过冷水
卷云
水云
Depolarization, The lidar, Elastic backscattering, Super-cooled water, Cirrus, Watercloud
