地球同步卫星资料的一种云地分离综合处理技术

An integrated processing technique on the detachment of cloud from the earth's surface using synchronous meteorological satellite data

利用多通道地球同步卫星资料,采用多通道阈值、基于晴空合成底图和云图时间序列的阈值和相似检测、有限区域动态阈值检测等方法,运用分步决策思路,对(60°S～60°N、45～165°E)区域内卫星云图分中高云和低云进行云地分离综合处理。经人工判断与自动云地分离结果对比分析表明,准确率达到90%以上。分析表明,考虑云和地(海)表在不同通道的亮温差异和随时间演变特点,建立并运用多种云地分离方法,有利于云地分离信息量的增加;提出的考虑云系分布时变特性的相似检测法,以及从有云和无云两个角度优先选择高可信度方法逐步检测,有利于云地分离准确率的提高。

Based on the decision tree method,an integrated processing technique on the detachment of cloud from the earth＇s surface with FY-2C multi-channel satellite data is performed step by step using three different measures,including the threshold method of multi-channel,the threshold method of similar test on time series of composed cloud/surface map derived from clear sky,and the limited regional dynamic threshold method.Experiments are made to fulfill the detachment of cloud map from the earth surface in the area of 60 S～60°N,45°E～165°E with FY-2C meteorological satellite data in July of 2005.In contrast with manual estimation,the detachment made by the computer automatically presents an accuracy rate over 90%.The analysis results show that,when taking the differences of the brightness temperature between the clouds and the earth surface（or the sea surface） into account as well as the characteristics of their temporal evolvements in different channels,the establishing and applying of multi methods on the cloud-surface detachment will be helpful to increase the quantity of information in detaching.These two approaches suggested in the paper—the similar test method which considers the varying characteristics with time of the clouds,and the stepwise test method which prefers to higher reliability under cloudy or non-cloudy circumstances—will be in favor of the detachment and its accuracy.