【作者】 王胜杰；

【导师】 王振会； 陈洪滨；

【作者基本信息】 南京信息工程大学 ， 大气遥感科学与技术， 2008， 硕士

【摘要】 云与辐射的相互作用对于全球的天气和气候变化过程有着重要的影响,不同高度的云有着不同的辐射强迫,获得云体高度及其在时空上的变化对于研究全球气候变化有着重要意义。云卫星(CloudSat)是世界上首颗专门用于研究云的卫星,首次从太空中对全球云层的垂直结构和云层的微物理特性进行观测,研究全球云层随季节和地理位置的变化,评估云层参数化在全球模式中的作用,从而有助于改进天气预报,解决气候及云与气候反馈作用中存在的问题。云卫星的主要载荷是天底观测的94GHz云廓线雷达(CPR),其横轨分辨率为1.4km,沿轨分辨率为2.5 km,垂直分辨率为500 m。本文利用云卫星上的云廓线雷达(CloudSat/CPR)2006年6月至2007年12月期间的资料,对比分析了青藏高原、高原南坡和南亚季风区域不同云类的云顶、云底高度和云体厚度统计量。结果表明,研究区域在单位面积上的云顶和云底高度变化具有一定的时空连续性,研究区域内不同云类的云顶和云底高度存在不同的变化区间,且随着季节的改变均有着明显的变化;同时各区域不同云类的云体厚度在夏季较大,冬季较小;各区域不同云类所占的比例(云量)随季节变化也具有一定的规律性;同类云体的云高和云厚特征量在不同的研究区域上是存在明显变化的。文中利用CloudSat资料获取云顶高度值、结合A-Train中Aqua卫星的MODIS云产品资料,对云顶高度与云顶亮温值之间的相关性进行了分析研究。通过大量的云层个例分析,结果表明,云顶高度值与云顶亮温值之间呈现负的相关系数,即亮温值随云顶高度的降低而增大;当云体分布较为密集连续,云体厚度较大时,亮温值与云顶高度之间具有较好的相关性。经过对比分析,设定了较为合理有效的判定阈值,从而获得了一个相对较好的云顶高度与云顶亮温间的相关系数,并拟合得到了线性经验公式。更多还原

【Abstract】 Cloud-radiation interaction has a large impact on the Earth’s weather and climate change, and clouds with different heights cause different radiative forcing. Thus, the information on the statistics of cloud height and its variation in space and time is very important to global climate change studies. CloudSat will provide, from space, the first global survey of cloud profiles and cloud physical properties, with seasonal and geographical variations, needed to evaluate the way clouds are parameterized in global models, thereby contributing to improved predictions of weather, climate and the cloud-climate feedback problem. The Cloud Profiling Radar (CPR) on CloudSat is a 94-GHz nadir-looking radar which measures the energy backscattered by clouds and precipitation within a 1.5 km across-track by 2.5 km along-track radar footprint and 500m vertical resolution.In this paper, cloud top height (CTH), cloud base height (CBH) and cloud thickness in the regions of Tibetan Plateau, Plateau south slope and South Asian Monsoon are analyzed based on the CloudSat data during the period from June 2006 to December 2007. The results show that frequency of cloud top and base heights in unit area over the studied regions have some certain space-time continuity. The CTH and CBH of different cloud types are in different range, and have significant seasonal variations. The cloud thickness is large (small) in summer (winter), and the percentage of different cloud types also have some certain regularity. The cloud heights and thicknesses of the same cloud type have some certain variation in the different study regions.We also use passive-sensing observation datas from the Moderate Resolution Imaging Spectroradiometer (MODIS) which boarded on Aqua (other A-Train satellite) to get the cloud top brightness temperature (TB) , and analyze the correlation between the MODIS TB and the CloudSat CTH. With a large number of cases, the results show that there is a negative correlation between TB and CTH, which means that the TB value will increase when the CTH is reduced. When the cloud is dense and thick, the correlation between the TB and the CTH is good. For improving the correlation, we set a more reasonable threshold to determine effective data. With this threshold, the correlation becomes much better, and a useful linear relationship is obtained.更多还原