【作者】 李志；

【导师】 田纪伟； 魏恩泊；

【作者基本信息】 中国海洋大学 ， 物理海洋， 2008， 博士

【摘要】 海表盐度是描述海洋的一个重要参量,研究其分布和变化规律对了解海洋自身特性以及海洋在海洋和大气这一复杂系统中的作用有着重要意义。海表盐度的遥感探测是获取该参量资料的有效手段。论文主要研究L波段海表盐度微波遥感机理和反演模式,该研究充分考虑了复杂的海洋状况及其环境要素,探讨了各种海况下盐度遥感反演的经验和理论模式。具体研究内容和创新成果如下:1、海面近似为平静表面前提下,论文分别考虑了法拉第旋转效应、大气传输、电离层吸收辐射等因素产生的亮温观测误差。结合辽宁庄河外海对比观测资料,本文首次综合考虑了法拉第旋转效应、大气传输和背景辐射等因素影响,建立了平静海面高精度的盐度遥感反演模式,平均绝对误差为0.4psu,和现有平静海面盐度反演算法比较,精度明显提高。目前模式通常将背景辐射这一时空变量当作常数处理,以及大气成份含量的多变性都可能产生海表盐度遥感反演的误差。未考虑真实海面的粗糙度影响也是导致盐度反演误差的重要原因。2、在低风速情况下,海表粗糙度是影响海面微波辐射亮温的重要因素。论文充分考虑了粗糙度,尤其是风速和涌浪的影响,结合北黄海海表盐度航空遥感比测实验数据,对风速和涌浪这两个参量进行线性回归,建立了适用于实验海区的高精度海表盐度反演模式,平均绝对误差为0.3。目前考虑粗糙度影响的海表盐度反演模式达到的最高精度为0.52psu,与此相比,本文所建立模式在实验海区反演结果更为精确。导致盐度反演误差可能是因为不同海区悬浮物、泥沙、海气温差等因素的影响,也正因如此海表盐度反演模式也具有一定的区域性限制。3、白冠覆盖海表盐度反演一直是盐度遥感反演的难点问题,目前白冠覆盖海面的盐度遥感机理和实验研究较少。论文针对白冠覆盖海表盐度反演机理进行了初步研究。由于海面白冠层是一种水气复合介质,因此对复合介质有效介电响应的研究十分必要。论文利用超几何方程,得到了球形粒子介电常数具有复杂形式的梯度复合物的有效介电响应解析公式,同时验证了DEDA(微分有效偶极子法)数值方法的有效性。在此基础上,利用有效介质近似理论方法,初步讨论了高海况条件下白冠覆盖率、气泡的粒径分布等因素对海表辐射率和海表盐度反演精度的影响。总之,真实海洋及其环境要素复杂多变,海洋物理参量之间也互相联系制约,如海水悬浊物、微生物、泥沙、海气温差等因素都可以改变海水的有效介电常数以及影响海表盐度反演精度,这些复杂的要素对盐度遥感的影响需要进一步深入探讨。更多还原

【Abstract】 The sea surface salinity is a key ocean parameter. Study of the distributions and variability of sea surface salinity is very important to understand the characteristics of the oceans and the role of the oceans in the complicated system of the ocean and atmosphere. The remote sensing exploration of the sea surface salinity is the most effective means to obtain the sea surface salinity datum. The paper mainly studies the L band remote sensing mechanism and retrieval model of sea surface salinity. The study takes into full considerations of the complicated condition of ocean and the environmental factors, and discusses the theoretical and experiential sea surface salinity retrieval mode under various sea conditions. The detailed content of the study and creativities are shown in the following.1. Under the quasi-calm sea surface condition, the paper has considered the errors of the brightness temperature respectively because of the effects of Faraday rotation, the atmosphere transmission, ionosphere’s absorption of radiation and so on. With the experimental datum of the outer sea of the Zhuang River of Liao-Ning, the paper primarily considered the effects of the environmental factors such as atmosphere propagation, background radiation etc., and established the high precise remote sensing retrieval algorithm. The mean absolute error of the retrieval salinity is 0.39psu, which is more accurate, compared with the present retrieval salinity of the other models. At present time, background radiation is treated as a constant in the retrieval model, but it’s a variant about the time and space in fact. Furthermore, the changeable density of the atmosphere components can also result in the error of the retrieval value of the sea surface salinity. The influence of the sea surface roughness for brightness temperature is also an essential factor which can lead to the salinity retrieval error.2. Under the low wind speed condition, the roughness of surface is the key element which influences the sea water brightness temperature. This paper fully considers the effect of the roughness, especially the influence of the wind speed and the ground swell. With the in-site measurements of the sea surface salinity and brightness temperature in the north Yellow Sea, the paper establishes the experimental sea surface salinity retrieval model for the experimental sea area. The mean absolute error of the retrieval salinity is 0.288psu. At present, the highest retrieval precision of the other models reaches 0.52psu. Therefore, the retrieval model in the paper is better than the others in the experimental sea area. The influence is probably to bring the error of the retrieval salinity, such as suspension objects, sand and the difference in temperature between atmosphere and ocean. Thereby, the sea surface salinity retrieval mode is regional restricted.3. Under the white cap covered sea surface condition, sea surface salinity retrieval is always a difficult problem. Nowadays, there is only little study about the sea surface salinity remote sensing theories and experiments about the white cap covered sea surface. This paper specially researches the mechanism of the sea surface salinity remote sensing retrieval about the white cap covered sea surface. On account of the white cap layer of sea surface that is a kind of composite media of water and air, it’s necessary to study the effective dielectric response of the composite. Employing the hypergeometric Equations, the paper gets the effective dielectric response analysis formula of graded composite with the graded spherical inclusion that has a complicated dielectric profile. At the same time, the paper verifies the validity of the DEDA (differential effective dipole approximation) method. Based on above results, the paper discusses the influence of the white cap cover rate and the bubble radial distribution for sea surface salinity retrieval under the high sea condition, by using the effective media approximation.In a word, the real ocean and its environment factors are complicated and various. Besides, these ocean physical parameters are relational and restricted each other. For instance, every factor among suspension objects, sand, animalcule, temperature difference can change the effective dielectric constant of seawater as well as influence the precision of sea surface salinity retrieval model. So, it is necessary to make a further study about the influence of these complicated environmental factors to the salinity remote sensing.更多还原