应用于O_2-A波段云检测的阈值选取方法

Threshold Selecting Method of Cloud Detection Applied to O_2-A Band

云污染直接决定了卫星数据用于反演的可行性,云检测是温室气体反演流程中的必要环节,阈值的选取决定了在O_2-A波段利用阈值法对卫星数据进行云检测的效果,如何获取最优阈值成为关键,目前的阈值选取大多数是经验法,缺乏系统考虑。提出了一种半经验阈值选取方法,根据晴空涵盖率和误判率构建优选函数,通过求取优选函数的极值实现了最优阈值的选取。利用GOSAT卫星数据进行算法验证的结果显示,相比于传统的经验统计法,该方法所选取的阈值应用于O_2-A波段云检测时,云判定的准确率提高近10%。

Cloud cover status determines whether satellite data can be used for retrieving or not.Cloud screening is essential in data processing flow of greenhouse gases retrieval.The threshold,whether appropriate or not,determines the accuracy of cloud detection in O2-A band via threshold method,methodology of how to obtain optimal threshold becomes a key-point requirement.Thresholds are selected based on empirical statistics that hence lack of systematism in most cases.A semi-empirical algorithm of threshold selection has been proposed,the algorithm construct a function by combining clear-sky contain ratio and false determinant ratio,then selecting the optimal threshold through seeking the maximum of this function.Finally,the algorithm was validated by GOSAT observation data and the result shows that,comparing with traditional statistical method,threshold determined by this algorithm increasing the cloud detection accuracy near upon 10 percent when applying it to O2-A band cloud detection.