【摘要】：長(zhǎng)江河口徑潮流相互作用,受徑流輸沙、本地泥沙再懸浮和波浪掀沙影響,水體中懸浮泥沙含量高啟,其中粒徑小于0.032mm的顆粒占絕大多數(shù),加之受鹽淡水混合作用的影響,細(xì)顆粒泥沙絮凝頻繁,給河口泥沙遙感反演精度的提高帶來(lái)困擾。泥沙絮凝改變了入水光線的傳播,從而導(dǎo)致離水輻射特性的改變,在建立衛(wèi)星遙感數(shù)據(jù)和水體組分的光譜定量關(guān)系時(shí),需要考慮這種泥沙絮凝及其解絮所致的離水輻射特性。本文研究擬通過(guò)長(zhǎng)江口上段、口門(mén)段和口外段的定點(diǎn)觀測(cè),獲取枯季現(xiàn)場(chǎng)表層絮凝體粒徑數(shù)據(jù)、光學(xué)數(shù)據(jù)和其他水文環(huán)境數(shù)據(jù),分析河口不同區(qū)段絮凝特性,探討絮凝體對(duì)實(shí)測(cè)光譜反射率的影響,為建立適合長(zhǎng)江口表層懸沙的反演模型,提高衛(wèi)星遙感對(duì)二類(lèi)水體監(jiān)測(cè)精度提供依據(jù)。根據(jù)不同區(qū)段的絮凝體粒徑的變化過(guò)程,對(duì)照同時(shí)間段內(nèi)流速、濁度和鹽度的變化過(guò)程,分析各個(gè)要素對(duì)絮凝體粒徑的影響。運(yùn)用主成分分析方法得到,絮凝體粒徑在河口上段受流速和濁度控制明顯,在口門(mén)段的小潮與河口上段類(lèi)似受流速控制,大潮則受鹽度控制,口外段則受鹽度控制。投影表面積作為衡量懸浮泥沙濃度和絮凝體平均粒徑的綜合變量,與懸浮泥沙濃度成正比,與絮凝體平均粒徑成反比。不同區(qū)段的絮團(tuán)組成成分、沉速、粒徑、有效密度和投影表面積都有較大的差異,枯季絮團(tuán)分散粒徑在空間上呈"小-大-小"分布,絮團(tuán)現(xiàn)場(chǎng)平均粒徑則呈"大-小-大"分布,沉速呈"大-小-大"分布,投影表面積呈"小-大-小"分布。除了懸浮泥沙濃度,現(xiàn)場(chǎng)測(cè)量的濁度、絮凝體平均粒徑和絮凝體投影表面積與光譜反射率都有較好的相關(guān)性,運(yùn)用多層感知器模型分析各個(gè)參數(shù)對(duì)遙感因子的貢獻(xiàn)率大小,并建立傳統(tǒng)的單因子回歸模型、考慮絮凝的多因子回歸模型和神經(jīng)網(wǎng)絡(luò)模型。結(jié)果表明,回歸模型中懸浮泥沙濃度的Gordon模型擬合情況較優(yōu),達(dá)到0.9091,神經(jīng)網(wǎng)絡(luò)模型擬合精度達(dá)到0.9688,預(yù)測(cè)性能最好,逼近真實(shí)情況。
[Abstract]:The Yangtze River channel tidal current interaction is affected by runoff and sediment transport, local sediment resuspension and wave sediment lifting, and the suspended sediment content in the water is high, in which the majority of particles with diameter smaller than 0.032mm are affected by the mixed action of salt and fresh water. The frequent flocculation of fine sediment makes it difficult to improve the precision of remote sensing inversion of sediment in estuaries. Sediment flocculation changes the propagation of incoming light, which leads to the change of radiation characteristics. In establishing the spectral quantitative relationship between satellite remote sensing data and water composition, it is necessary to consider the characteristics of water leaving radiation caused by the flocculation of sediment and its deflocculation. In this paper, the surface flocculant particle size data, optical data and other hydrological environment data of the upper, outer and outer segments of the Changjiang Estuary are obtained, and the flocculation characteristics of different sections of the estuary are analyzed. The effect of flocculation on the measured spectral reflectance is discussed in order to establish the inversion model of suspended sediment on the surface of the Changjiang Estuary and to improve the precision of satellite remote sensing monitoring of the second kind of water body. According to the changing process of flocculant particle size in different sections, the influence of each factor on the particle size of flocculant was analyzed by comparing the change process of flow rate, turbidity and salinity in the same time period. By using principal component analysis method, the particle size of flocculant is controlled by velocity and turbidity obviously in the upper section of the estuary, the small tide in the mouth gate section is controlled by the velocity of velocity similar to that in the upper section of the estuary, the large tide is controlled by salinity, and the outside section is controlled by salinity. The projection surface area, as a comprehensive variable to measure the suspended sediment concentration and the average particle size of flocculants, is directly proportional to the suspended sediment concentration and inversely proportional to the average particle size of the flocculants. The composition, settling speed, particle size, effective density and projection surface area of flocs in different sections are all different. In the dry season, the dispersion particle size of flocs is "small-big-small" distribution. On the other hand, the average particle size of flocs is "big-small-large" distribution, sedimentation velocity is "big-small-big" distribution, projection surface area is "small-big-small" distribution. In addition to suspended sediment concentration, the turbidity, mean particle size and projected surface area of flocculants were all correlated with spectral reflectivity. The multilayer perceptron model was used to analyze the contribution rate of each parameter to remote sensing factors. The traditional single factor regression model was established, and the multifactor regression model and neural network model were considered. The results show that the Gordon model of suspended sediment concentration in the regression model is better, reaching 0.9091, and the fitting precision of the neural network model is 0.896. The prediction performance is the best and the model is close to the real situation.
【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：P332.5

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