全天空成像辐射仪对云和天气的地基遥感

【作者】 霍娟；

【导师】 顾松山； 吕达仁；

【作者基本信息】 南京气象学院 ， 大气物理学与大气环境， 2002， 硕士

【摘要】 根据发展自动化云观测的目标，利用云和晴空大气在可见光／近红外、热红外多波段散射辐射和热辐射的不同特征，我们尝试建立一个多波段(可见／近、热红外)全天空成像辐射观测系统，进行全天空分波段成像辐射的获取，定量分析和特征识别，获得云量、云型、云底高信息，实现对云参数化信息的自动获取。本论文主要开展可见光波段的研究，论文内容主要包括三个部分： 第一部分，简单介绍数字图像处理的基本概念和基本原理。说明了图像资料的采集情况。 第二部分，对全天空数字图像进行详细分析与研究，总结出基本的大气成像规律。一般晴好天气情况下，像素灰度值中蓝色成分占0.375以上的是蓝天，而小于0.345的是白云。气溶胶粒子含量丰富时，大气与云间的区别变小，规律不易寻找，在本文中采用了其它的手段进行分析。 第三部分，依据分析所获得的大气成像规律，通过图像估算云量、辨别云型、分析辐射分布等。结果分析表明，云量的计算结果受能见度影响程度大，晴好天气下云量的计算同观测员记录比较误差在10％左右。同模式的计算结果相比，大气辐射分布分析虽然能够表现出辐射的分布状况，但是缺乏定量描述。文章最后还对三个拍摄基地的大气图像各自的成像特性做了相互分析与比较。更多还原

【Abstract】 In this paper a system has been developed for studying characteristics of "clouds and sky" on the images taken by a whole-sky camera at three different wave bands (the visible, the infrared, long wave infrared), then assessing the presence, distribution, shape, and radiance of clouds over the entire sky using automated cloud decision algorithms and related processing. This study lays focuses on the visible-light spectrum, and it is composed as follow:In first part, the fundamental principles and theories of the digital image processing are presented.The second part shows the methods in detail of analyzing and processing all the images. We find that the sky pixel’s blue /brightness (red, green and blue) ratio is always more than 0.375 and the cloud pixel’s is less than 0.345 when the day is fine. But it is difficult to get rules of those images, which are taken in the condition of the occurrence with a great deal of aerosol in the sky. Such images are analyzed by employing the other methods in the study.Finally, the paper presents the results after processing images data. It includes estimating the cloud-cover, and describing cloud shape, analyzing radiation distribution of clear-sky. The estimation of cloud-cover is mainly affected by the visibility of the day. Comparing the calculated results from about 350 images to the observation, the average error is about 10%. We also compare the analysis of radiance to the one analyzed with a model, they fits very well. But we can’t describe the radiance quantificationally at present. At the end of the paper, some differences between those images taken at three different places are analyzed.更多还原