【作者】 邓孺孺；

【导师】 田国良；

【作者基本信息】 中国科学院研究生院（遥感应用研究所） ， 地图学与地理信息系统， 2002， 博士

【摘要】 地表反照率是影响地表能量收支平衡的决定性因素之一，青藏高原具有极高的海拔和广阔的面积，其反照率对地区乃至全球的大气运动及气候有重要影响。本文的目的是对青藏高原地表反照率和冷热源参数进行定量反演。为获得较高的反演精度，采取象元组分信息分解的方法，将象元对应地物分解为土壤、植被、水分、水体、雪被等基本组分，然后根据这些组分的光谱组合模型用遥感数据计算象元中各组分含量，再根据组分含量反演半球反射率和反照率。 为建立象元组分信息模型，本文对土壤光谱与土壤含水量及表面粗糙度的关系进行了深入研究，论证了含水量与土壤光谱呈指数关系，提出了土壤含水量与土壤光谱的函数关系式，并测定了土壤水吸收系数；在研究土壤光谱反射与散射过程基础上，提出了土块级土壤粗糙度与土壤光谱的函数关系式，进而提出了湿润、粗糙土壤反射率的数学模型，并通过实验证明了模型具有较高的精度。 在植被反射率模型方面，本文根据青藏高原植被特点，对Hapke’s等的植被冠层模型进行了改进，提出了更为实用的植被冠层模型。模型考虑前三次散射，既保证了计算精度，又减小了运算量。 地形与反射率的关系是本文研究的一个重点。本文对崎岖山地象元的各入射光和反(散)射光分量进行了深入分析，在所提出的湿润土壤光谱模型和植被冠层模型的基础之上进一步提出了新的适合青藏高原的山地辐射传输模型。该模型同时考虑了土壤含水量、植被覆盖(LAI)、地形起伏和海拔高度的影响，并以象元坡面定义的半球空间立体角对环境入射光进行积分，使周围地形和天空散射光均得到适当考虑，计算量又在可接受范围内。 在以上提出的山地辐射传输模型基础之上，对Irons等提出的10波段反照率计算方法进行了发展，提出了高原山区的反照率计算模型。并应用该模型对多时相的青藏高原反照率进行了计算。得到了比传统方法精度更高的结果。对反照率及其变化进行分析，发现反照率的总体分布与地形及雪域密切相关。地形伏大的山坡、山麓地区，反照率明显降低，山顶雪域分布区反照率显著上升。高原反照率年变化的主要原因是土壤含水量、雪盖分布面积及植被覆盖度的变化。 然后，在翁笃鸣等提出的有关半经验公式的基础上，提出了根据反照率和地形参数计算高原地面向大气输送能量的日平均通量的算法，并以此作为判定冷热源的标准。用该方法对青藏高原1998年夏天、2000年夏至和冬至晴空条件下地面向大气的输送能日平均通量进行了计算。结果显示，地形与输送能日平均通量成正相关，青藏高原四季均为热源。夏季，整个高原为一强热源，其中高原南部为极强热源;冬季，高原南部为强热源，而北部则减弱为弱热源。 最后针对青藏高原热力作用对气候的影响进行了分析。得到的结论是，高原的热源作用使高原上空形成一个大气对流系统，作用强时可形成反气旋，弱时在高原上空形成对流云系。在高原热力用和地形的共同作用下，来自西南或西面的潮湿空气在高原迎风坡面中部被抬升，两侧被地形分开，导致在高原南部和两侧的中国南方及印度一孟加拉地区雨量丰沛，而高原北面的中国北方则形成异常干旱的气候。该结论得到了大范围的GMS卫星图像云图和水汽分布图系列的验证。更多还原

【Abstract】 Albedo is one of the most important factor which effect the balance of the outing and incoming solar energy of ground surface. Because Tibetan Plateau has the highest elevation on the world and a vast area, its albedo performs a most important influence to the atmospheric motion and climate of the region, and even of the globe. The objective of this paper is to retrieve the albedo of the plateau and then to calculate the parameters about hot or cold source quantitatively. To gain a higher precision of retrieval, the method of pixel information decomposition is introduced in. The method is to divide ground objects correspond to a pixel in to several basic components: soil, vegetation, moisture, water, and ice, and then, using remote sensing data, calculate the contents of every components according to the model by which the component’s spectrum compose. After that semi-globe direction reflectance and albedo of pixel are calculated according to the contents of every component.For that, the relationship between soil spectrum and water content and the roughness of soil surface are deeply studied in the paper. And the exponent relation between water content and soil spectrum are demonstrated, then the function of water content and soil spectrum are put forwarded, and the curve of absorption coefficient of water content in soil measured. Basing the study on the course of reflection and scattering taking place on soil surface, a function of relation between soil spectrum and the roughness of clod was put forwarded. Then a mathematic model on the relation between soil spectrum and water content and surface roughness are proposed. The model was verified by experiment.To the aspect of bi-directional reflection distribution function of vegetation, according to the characteristics of the vegetation over Tibetan Plateau, a new model was proposed by improve Hapke’s model to consider the scattered flux of the first three times, which obviously promote the precision, but the amount of calculation is reduced.To the influence of the plateau terrain, the impact of the elevation and the roughness of terrain to every energy component out and incoming are study, and basing the soil spectrum model proposed above, a new radiative transfer model of terrain area was put forwarded in which the soil water content, LAI, terrain roughness and elevation were considered synchronously, and incoming scatter light was integral with the solid angle of semi-globe space defined by the slope of the pixel, soscattering lights of terrain and the sky are properly considered, but the operation is still within the acceptable range.Basing the radiative transfer model of terrain area, a new model for calculating the albedo over terrain area was put forwarded by improve Irons’ model of albedo calculation with 10 spectrurns. Using this model, albedos over Tibetan Plateau of different time were calculated. The results of albedo have higher precision than that get by traditional method. The result images showed that the distribution of albedo has a close connection with terrain and snow. Rough terrain areas have lower albedo, when albedo on snow area is much higher than other area. By comparing the albedo image of winter and summer, it is shown that albedo of Tibetan Plateau in winter is obviously large than that of in summer. The cause is that there are large distribution areas of moistly soil, wetly lands, and vegetative land, and smaller area of snow on the plateau.Then basing the empirical formal proposed by Weng Burning, a method for reckon the average flux of energy transfer from ground surface to the air of a day according albedo and terrain parameters was put forwarded. It is considered that the flux is a proper index to decide if the area is a hot source or a cold source. The average flux of energy transfer from ground surface to the air of a day of Tibetan Plateau in summer, 1998; the Summer Solstice and midwinter, 2000 are calculated. The results show that the flux has a positive relationship with elevation, and that, Tibetan Platea更多还原