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学科主题: 地理学::自然地理学
题名: 青藏高原地表特征参数地基观测与卫星遥感反演研究
作者: 仲雷
答辩日期: 2007-12-28
导师: 马耀明
专业: 自然地理学
授予单位: 中国科学院研究生院
授予地点: 北京
学位: 博士
关键词: 辐射平衡 ;  能量平衡 ;  地表反照率 ;  地表温度 ;  植被指数 ;  AVHRR ;  MODIS ;  SPOT ;  青藏高原
索取号: B000006
部门归属: 图书馆
摘要: 被喻为“世界屋脊”和“地球第三极”的青藏高原,由于其高大的地形特征和高原下垫面所吸收的太阳辐射能,使得该地区地气相互作用过程,尤其是能量与水分循环过程对亚洲季风、东亚大气环流及全球气候变化均有极大的影响。长期以来,由于高原恶劣的自然条件,很难对地表特征参数和地气能量交换特征进行系统观测,现有的观测数据历史较短,观测站点较为稀疏而且分布不均,使得人们对高原地表特征知之甚少。随着“全球能量水循环之亚洲季风青藏高原试验研究” (GAME/Tibet)和“全球协调加强观测计划(CEOP)亚澳季风之青藏高原试验研究”(CAMP/Tibet)的顺利实施以及一批综合观测台站在高原的相继建立,获得了大量珍贵的大气观测资料,为研究不同下垫面条件下的高原地表参数变化特征与地气相互作用奠定了数据基础。同时卫星遥感技术的发展为获得青藏高原面上的地表特征参数提供了一种可能手段。本论文主要包括三个方面的研究内容,首先在地表参数地基观测研究方面,选取CAMP/Tibet试验区的NPAM站和珠穆朗玛峰北坡QUZONG地区大气湍流观测试验资料,分析了藏北高原地区和珠峰北坡地区辐射平衡分量的日变化及其季节变化特征。在辐射平衡观测资料基础上,对比分析了两地区地表反照率的日变化和季节变化特征。然后分别利用组合法和涡旋相关法计算得到了藏北高原地区和珠峰地区的能量平衡各分量,进而对比分析了两地区干湿季地表能量平衡特征变化。通过分析发现两地区辐射平衡分量、地表反照率以及能量平衡各分量的日变化和季节变化都很明显。但由于所处地理环境不同,两地区地表参数也有很大不同。具体表现在,QUZONG地区获得的太阳短波辐射和地面反射的短波辐射均大于NPAM地区。NPAM地区的大气长波辐射、地面长波辐射以及净辐射均高于QUZONG地区。两地区地表反照率的日变化和季节变化曲线均呈“U”型,但QUZONG地表反照率始终高于NPAM。研究发现,干季,QUZONG土壤相对湿润,其潜热通量大于NPAM,而感热通量小于NPAM;湿季,NPAM的潜热通量大于QUZONG的潜热通量,而NPAM的感热通量则小于QUZONG。在珠峰大气湍流观测的基础上,进行了湍流统计特征分析,证实珠峰北坡地区Monin-Obukhov相似定律同样适用并且得到了风速各分量、温度和湿度归一化标准差随大气静力学稳定度的变化关系。这些地面观测资料的分析结果为卫星遥感分析青藏高原的地表特征参数打下了良好的基础。其次,在遥感反演方面,分别利用中分辨率成像光谱仪(MODIS) L1B数据和甚高分辨率辐射仪(AVHRR) L1B数据,筛选出2003年1月17日、4月14日、7月23日和10月16日影像作为高原冬季、春季、夏季和秋季代表,经过辐射定标、可见光和近红外波段的太阳高度角校正、几何校正、图像镶嵌裁剪等系列处理后,利用简化的大气校正方法(SMAC)对遥感影像进行了大气校正,最后经过窄带反照率向宽带反照率转换环节,反演得到青藏高原地区地表反照率空间分布和季节变化图像。在地表温度反演方面,分别对AVHRR和MODIS反演得到基于像元的地表比辐射率和大气水汽含量,利用分裂窗算法得到高原地表温度空间分布和季节变化图像。在此基础上利用藏北高原四个地面观测站(D105、ANNI、BJ、NPAM)的地面实测资料对反演结果进行了验证。论文最后针对遥感影像云污染问题严重这一实际问题,在最大值合成的基础上,利用时间序列谐波分析(HANTS)算法对SPOT 2003年全年NDVI遥感影像进行时间序列处理,得到无云污染的NDVI时间序列图像。并选取青藏高原两处典型下垫面植被覆盖,对比分析了HANTS处理前后NDVI变化情况。研究结果表明,HANTS算法能够有效的对遥感影像进行去云处理和无缝插值,所得结果和地表实际情况相符。
英文摘要: The Tibetan Plateau is often called the “World Roof” and “The Third Pole” on the earth. Because of its great topographic characteristic and the large amount of solar energy it absorbs, the land-atmosphere interaction over this area, especially the energy and water cycle, has great influence on the Asian monsoon, east Asian atmospheric circulation and even the global climate changes. For a long time period, it’s very difficult to carry out systematic observation of the surface characteristic parameters and the energy fluxes exchange between the land surface and atmosphere. The history of existing observation is rather short and the observation sites over the Tibetan Plateau are not only sparse but also uneven. Therefore, little has been known about the surface characteristics of the Tibetan Plateau. However, with the implement of GEWEX Asia Monsoon Experiment on the Tibetan Plateau (GAME/Tibet), Coordinated Enhanced Observing Period (CEOP) Asia-Australia Monsoon Project on the Tibetan Plateau (CAMP/Tibet) and some new observation stations being set up over the Tibetan Plateau, a large amount of valuable atmospheric data has being achieved. This forms the data base for the study of variation of surface parameters and the land-atmosphere interaction. Simultaneously, the fast development of remote sensing technique provides a good method to study the regional surface characteristics over the Tibetan Plateau area. Three research aspects are included in this thesis. The first one is ground-based observation study of surface parameters. Based on the observation data of NPAM in CAMP/Tibet experiment area and the atmospheric turbulent data collected at QUZONG, on the northern slope of Mt. Everest, the diurnal and seasonal variation characteristics of radiation balance and energy balance components are derived. On the basis of radiation data, the diurnal and seasonal characteristics of surface albedo are compared between NPAM and QUZONG. Then the energy balance components over the northern Tibetan Plateau area and the northern slope of Mt. Everest are achieved with synthetic method and eddy correlation method respectively. The variation characteristics are compared with each other. The results show that the diurnal and seasonal variation of radiation balance components, surface albedo and energy balance components are very clear. However, because of the different natural environment where the two stations locate, the surface parameters there are a little different from each other. This can be elaborated by the following facts. The downward shortwave radiation and upward shortwave radiation at QUZONG are much higher that those at NPAM. The downward longwave radiation, upward longwave radiation and the net radiation at QUZONG are less than those at NPAM. The diurnal and seasonal variation of surface albedo at these two stations is characterized by “U” shape. The surface albedo at QUZONG is always higher than NPAM. The study also reveals, in dry season, the soil at QUZONG is relatively wet. The latent heat flux there is greater than NPAM, however, with the sensible heat flux less than NPAM. In wet season, the lantent heat flux of NPAM is greater than QUZONG with the sensible heat flux less than QUZONG. Based on the atmospheric turbulence observation at QUZONG, the turbulent statistical analysis is carried out. The results show that Monin-Obukhov Similarity Theory is also fit for this area. The non-dimensional standard deviation of wind velocity components, temperature and humidity as a function of atmospheric stability parameter is derived. These results are the base to study the regional land surface parameters over the Tibetan Plateau by using the satellite data. Secondly, for the retrieval of surface parameters from remote sensing, based on the MODIS L1B and AVHRR L1B data, several satellite images are chosen as the representation cases of winter, spring, summer and autumn. The images are taken on January 17, April 14, July 23 and October 16 in 2003. After the radiation calibration, the solar elevation angel correction of the visible and near infrared band, geometrical correction, image mosaic and subset, the atmospheric correction through Simplified Method for the Atmospheric Correction (SMAC) is carried out. The spatial distribution and seasonal variation patterns of land surface albedo are achieved after the last processing from the narrowband to broadband conversions. As for the retrieval of land surface temperature, the pixel-based land surface emissivity and atmospheric water vapor content are derived first from the satellite images of AVHRR and MODIS. Then the split-window algorithms are applied to achieve the spatial distribution and seasonal variation maps of land surface temperature. The results are compared to the ground measurements from four validation sites of D105, ANNI, BJ and NPAM in CAMP/Tibet area. The cloud contamination is a serious problem to the application of satellite images especially over large area of Tibetan Plateau. Based on the Maximum Value Compositing (MVC) method, apply Harmonic ANalysis of Time Series (HANTS) algorithm to do time series analysis of SPOT NDVI data of 2003. The time series of NDVI images free of cloud contamination are achieved. Two typical land cover types over the northern and eastern part of Tibetan Plateau area are chosen to compare the NDVI variations before and after HANTS processing. The results show HANTS is an effective tool to remove the cloud contamination from the original satellite images and it can also interpolate right values at the pixels contaminated by cloud. The results from HANTS algorithm are fairly coherent with the land surface conditions.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.itpcas.ac.cn/handle/131C11/1224
Appears in Collections:图书馆_学位论文

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Recommended Citation:
仲雷.青藏高原地表特征参数地基观测与卫星遥感反演研究[博士].北京.中国科学院研究生院.2007
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