卫星主动观测的视线云出现频率特征分析

Cloud Occurence Frequency along the Line of Sight Derived from Satellite-based Active Measurements

云对气象、测绘、国土资源调查等领域中空基和天基光学、红外传感器的使用有着显著影响。为了分析中国及周边区域不同高度上各视角方向的云出现频率,首先建立了基于卫星主动观测的视线云出现频率计算模型,并利用2006年7月至2009年3月的CloudSat/CALIPSO联合观测资料,对中国及周边地区不同高度多个方向上的云出现频率分布进行统计分析。结果表明:视线上云的出现频率因观测高度、角度的不同而不同,且具有明显的季节变化特征,但观测结果具有方位独立性。在各高度,视线由水平方向移向垂直向下时,云出现频率在某一观测方向存在极小值。此外,对比分析了指定高度上的云出现频率分布特征,结果表明:各高度上的云出现频率分布存在明显的地区差异,在对流层上层,云出现频率与纬度相关,且在热带区域存在局地极大值。

Clouds have significant impacts on the use of the facilities for optical, infrared and microwave ob- servations and communications in the fields of meteorology,topography,and land resource survey. In order to analyze the cloud occurrence frequency along the line of sight over China and its neighborhood, the calcu- lation method based on active measurements is developed. Then,the CloudSat/CALIPSO observations from June 2006 to March 2009 are used and analyzed. The results show that the cloud occurrence frequency is strongly dependent on the view angle, altitude and season. Furthermore, it reveals that the cloud occurrence frequency along the line-of-sight is independent of the azimuth. In the scope of the downward observations, there is a minimum cloud occurrence Frequency value at a particular angle. Additionally, the cloud occur- rence Frequency distributions at different heights are also analyzed. This paper shows that the cloud occur- rence significantly differs over different areas. Especially, it strongly depends on the latitude in the upper troposphere, but there are some maximums over tropical regions.