渤海海洋悬浮泥沙二元特征参数MODIS遥感反演模型研究

This paper brought out a new idea on the retrieval of suspended sediment concentration, which uses both the water-leaving radiance from remote sensing data and the grain size of the suspended sediment. A principal component model and a neural network model based on those two parameters were constructed. The analyzing results indicate that testing errors of the models using the two parameters are 0.256 and 0.244, while the errors using only water-leaving radiance are 0,384 and 0.390. The stability of the models with grain size parameter is also better than the one without grain size. This research proved that it is necessary to introduce the grain size parameter into suspended sediment concentration retrieval models in order to improve the retrieval precision of these models.     

基于半分析模型的渤海湾近岸海域悬浮泥沙浓度遥感反演

悬浮泥沙浓度是海洋质量和环境评价的重要参数之一,遥感技术可以实现对海洋水色要素基础信息实时、连续、大范围监测,是当前大尺度海洋生态环境监测的重要手段。然而,现今并没有一个通用的模型可以实现对所有复杂水体悬浮泥沙浓度的反演。该文基于野外站点观测、结合研究区水体光谱特性,构建了基于多波段准分析算法(QAA)的渤海湾近岸海域悬浮泥沙浓度遥感反演半分析模型,并利用Landsat TM遥感数据,对研究区悬浮泥沙浓度进行了反演,制作了悬浮泥沙浓度空间分布图。研究结果显示,该文构建的半分析模型与前人研究的经验统计模型相比,具有更高的精度和普适性,相对误差达到18.28%;研究区的悬浮泥沙浓度整体较低,平均泥沙浓度为27mg/L,且呈现近海大于远海、南部海域大于北部海域的规律。     

基于RS的龙羊峡库区悬浮泥沙分布研究

依据含沙水体的光谱特性,在可见光的任一波段内,水体中的含沙量与水面光谱反射率成正相关关系。研究表明TM2和TM3波段能够较好的反映水体悬浮泥沙的含量,并且TM2+TM3能使水体泥沙含量差异更显著。据此以龙羊峡库区为例,通过对该区两个时相的TM影像进行水体提取、二值化、掩膜、密度分割等处理,提出了一种悬浮泥沙分布的方法。经过对比分析表明该方法可以充分利用TM数据,在缺乏足够实测数据的情况下,可以有效、快捷地得到层次丰富的泥沙分布图。     

长江口水域多光谱遥感水深反演模型研究

利用Landsat-7 ETM 遥感影像反射率和实测水深值之间的相关性可以探测水深。该文介绍单波段、双波段比值和多波段3种线性回归模型以及动量BP人工神经网络水深反演模型。选择长江口北港河道上段作为研究区,利用上述模型,分两种情况进行水深反演:一是以河道全部历史样本建模;二是将河道按自然水深划分为浅水区和深水区分别建模。结果表明:神经网络模型预测精度高于线性回归模型;水深分区后线性回归和神经网络模型预测误差均有所减小。     

基于多策略的极地遥感反演模型集成研究

极地遥感反演模型是极地研究的一种非常重要的工具.遥感反演模型对极地研究具有重要性,分析遥感反演模型的特点,以持续性、业务化、统一调用为目标,提出极地遥感反演模型集成应用架构.基于该集成方案,提出基于多策略的模型改造方法,并从三个方面详细论述模型的集成模式.基于可执行程序的模型改造方法对模型进行改造,采用应用端的模型集成...     

基于MODIS的青藏高原湖泊透明度遥感反演

湖泊透明度是湖泊水体性质的一个重要参数,是湖泊浮游生物和进入湖泊的有机和无机颗粒溶解程度的综合反映,对湖泊生态环境研究具有重要的科学及实践意义。遥感影像是获取面积广、时间长的湖泊透明度的重要手段,但由于实测数据缺乏,目前对青藏高原地区湖泊透明度的遥感反演研究相对不足。本文基于青藏高原地区24个湖泊实测透明度SD(Secchi Depth)值和相应的MODIS遥感影像,建立了该地区湖泊水体透明度SD值MODIS遥感反演模型。结果表明：基于MODIS绿色波段B4的单波段幂函数模型在该地区反演效果最好,精度较高(R2=0.91, N=24),并具有较好的稳定性。以当惹雍错为例,选用该模型反演得到湖泊透明度的时间变化序列,发现该湖存在明显的季节波动和较为明显的年际变化。初步分析得出,降水/融水季节的湖泊透明度与湖泊所在流域的降水率具有密切的关系。本文结果表明,利用遥感手段能够有效地开展青藏高原地区湖泊透明度的反演,可为进一步深入研究该地区湖泊透明度及其影响要素奠定基础。     

珠江河口潮周期泥沙动态输移特征遥感反演分析

珠江河口属粤港澳大湾区核心水域,战略位置重要,区内河网密布交错,河道、河口区径流与潮流相互作用,泥沙运动较为复杂。泥沙输移是河床演变的物质来源,直接关系到粤港澳大湾区防洪、供水、航运安全。文章利用高分四号卫星高频次影像数据开展珠江河口区潮周期内水表层泥沙定量反演,结合野外观测数据,以枯季2019-12-28及洪季2020-06-20两期多时相数据为例,探究潮周期内珠江河口泥沙含量时空分布。结果表明,高分四号卫星影像数据大气校正平均绝对百分比误差为18.85%;基于高分四号卫星影像数据近红外、红波段与蓝波段比值构建了泥沙反演模型,实现对珠江河口区间隔2 h日变化尺度泥沙输移连续动态监测,其中洪、枯季最优模型MAPE误差分别为30.00%、23.54%。反演结果能较为形象地展示河口区整体泥沙动态输移特征,与实测站点泥沙质量浓度相比,反演结果在潮周期泥沙质量浓度变化趋势上相一致,实现了珠江河口区径潮作用下面上泥沙动态输移的特征分析。该方法为复杂河口泥沙输移大范围业务化监测提供了新的思路,同时为珠江河口泥沙输移数值模拟与遥感监测提供了交叉验证的新思路。     

基于MODIS遥感定量反演的松嫩平原生态环境要素

以MODIS遥感影像为基础,在各种气象参数和遥感空间建模的支持下,应用定量遥感反演技术,获取了松嫩平原植被覆盖度、土壤湿度、陆面温度和植被净初级生产力四种生态环境要素的空间分布栅格影像。通过应用GIS空间分析功能,总结了各种生态环境要素的空间分布规律,并对植被覆盖度与土壤湿度、陆面温度和植被净初级生产力之间的相关性分别进行了定量研究。     

地表蒸散遥感反演双层模型的研究方法综述

通过遥感方法反演表面温度来计算地表蒸散量是定量遥感的一个很有潜力的应用领域。这种方法已成功地应用于植被完全覆盖的地表蒸散的监测,然而对于植被稀疏的地区,利用该方法模拟通量和观测通量之间存在很人的差异。产生这种差异的原因是假设辐射表面温度可以用来代替空气动力学温度。在这种假设条件下,植被完全覆盖的地表的通量计算能够得到较为满意的结果,但对于稀疏植被地表却是不成立的。对此,国内外许多学者提出了将土壤和植被分开计算的双层模型以求得到更加准确的通量结果。介绍了当前国内外几种常用的地表蒸散遥感估算双层模型,讨论了这些模型的物理基础和假设并讨论了目前双层模型在计算通量时存在的一些问题和难点,并对今后的工作重点和研究方向提出了建议。     

南黄海辐射沙洲邻近海域表层悬浮颗粒物浓度遥感反演

利用2003年春、秋季南黄海辐射沙洲邻近海域水体表观光谱测量与同步水体取样数据,分析该海域不同季节表层水体遥感反射率光谱响应特性。结合常用水色传感器波段光谱响应模拟,建立春、秋季表层水体总悬浮颗粒物浓度(TSM)与悬浮泥沙浓度(SSC)的最适单波段、双波段(波段比值)和3波段统计反演模式。结果表明,不同季节水体上述3类算法的最优波段均不相同,欲寻求适合所有季节水体的统一反演算法,仅能选择次优波段。通过比较,3种不同反演模式中三波段模式更适于反演近岸水体悬浮颗粒物浓度。     

Feasibility study on the binary-parameter retrieval model of ocean suspended sediment concentration based on MODIS data

This paper brought out a new idea on the retrieval of suspended sediment concentration, which uses both the water-leaving radiance from remote sensing data and the grain size of the suspended sediment. A principal component model and a neural network model based on those two parameters were constructed. The analyzing results indicate that testing errors of the models using the two parameters are 0.256 and 0.244, while the errors using only water-leaving radiance are 0.384 and 0.390. The stability of the models with grain size parameter is also better than the one without grain size. This research proved that it is necessary to introduce the grain size parameter into suspended sediment concentration retrieval models in order to improve the retrieval precision of these models.     

长江口悬沙浓度变化的同步性和差异性

近年来长江流域入海沙量呈现阶梯性减小趋势,三峡水库蓄水后加剧了这一减小趋势,并通过传递效应影响河口悬沙浓度变化。基于长江口1950-2013年悬沙浓度数据,结果表明：① 长江口南支河段及口外海域悬沙浓度为减小趋势,且越向海域减幅越小,同时与流域入海沙量减幅差距加大;② 北支优势流变化不大,但悬沙浓度为减小趋势,主要为南支和海域大环境悬沙浓度减小所致;③ 拦门沙河段悬沙浓度的峰值区域因径流减小、潮流相对增强,2003-2012年较1984-2002年期间峰值位置向口内上溯约1/6经度,上溯距离洪季 > 年均 > 枯季;④ 1999-2009年南槽进口悬沙浓度减小,主要是再悬浮和滩槽交换引起的悬沙浓度增量小于流域和海域悬沙浓度锐减引起的减量,中段该作用相反,悬沙浓度为增加趋势;⑤ 北槽进口由于分流分沙比减小、流域和海域悬沙浓度减小及再悬浮量减小等综合影响下,1999-2012年逐年的8月份悬沙浓度呈减小趋势,中段越堤沙量作用明显高于外部坏境引起的减小量,为增加趋势。     

Temporal and spatial changes of suspended sediment concentration and resuspension in the Yangtze River estuary

A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion of the hydrodynamic regimes of the estuary. Spatially, the SSC from Xuliujing downwards to Hangzhou Bay increases almost constantly, and the suspended sediment in the inner estuary shows higher concentration in summer than in winter, while in the outer estuary it shows higher concentration in winter than in summer, and the magnitude is greater in the outer estuary than in the inner estuary, greater in the Hangzhou Bay than in the Yangtze River estuary. The sediments discharged by the Yangtze River into the sea are resuspended by marine dynamics included tidal currents and wind waves. Temporally, the SSC shows a pronounced neap-spring tidal cycle and seasonal variations. Furthermore, through the analysis of dynamic mechanism, it is concluded that wave and tidal current are two predominant factors of sediment resuspension and control the distribution and changes of SSC, in which tidal currents control neap-spring tidal cycles, and wind waves control seasonal variations. The ratio between river discharge and marine dynamics controls spatial distribution of SSC.     

长江口水域悬沙浓度时空变化与泥沙再悬浮

A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion of the hydrodynamic regimes of the estuary. Spatially, the SSC from Xuliujing downwards to Hangzhou Bay increases almost constantly, and the suspended sediment in the inner estuary shows higher concentration in summer than in winter, while in the outer estuary it shows higher concentration in winter than in summer, and the magnitude is greater in the outer estuary than in the inner estuary, greater in the Hangzhou Bay than in the Yangtze River estuary. The sediments discharged by the Yangtze River into the sea are resuspended by marine dynamics included tidal currents and wind waves. Temporally, the SSC shows a pronounced neap-spring tidal cycle and seasonal variations. Furthermore, through the analysis of dynamic mechanism, it is concluded that wave and tidal current are two predominant factors of sediment resuspension and control the distribution and changes of SSC, in which tidal currents control neap-spring tidal cycles, and wind waves control seasonal variations. The ratio between river discharge and marine dynamics controls soatial distribution of SSC.     

The synchronicity and difference in the change of suspended sediment concentration in the Yangtze River Estuary

The sediment discharge from the Yangtze River Basin has a stepwise decreasing trend in recent years. The impounding of the Three Gorges Reservoir exacerbated this decreasing trend and affected the change of the suspended sediment concentration (SSC) in the Yangtze River Estuary through the transmission effect. The SSC data of the Yangtze River Estuary during 1959-2012 showed that: (1) The SSC in the South Branch of the Yangtze River in the estuary and in the off-shore sea area displayed decreasing trends and decreased less towards the sea. At the same time, the difference in decreasing magnitude between SSC and sediment discharge became bigger towards the sea. (2) For the North Branch the preferential flow did not change much but the SSC tended to decrease, which was mainly caused by the decrease of SSC in the South Branch and China East Sea. (3) Due to the decreased runoff and the relatively strengthened tide, the peak area of the SSC in the bar shoal section in 2003-2012 moved inward for about 1/6 longitude unit compared with that in 1984-2002, and the inward-moving distance was in the order of flood season > annual average > dry season. (4) In the inlet of the South Passage, the SSC decreased mainly because the increase caused by resuspension and shore-groove exchange was less than the decrease caused by the sharp SSC decrease in the basin and the sea areas. The reverse was true in the middle section, where the SSC showed an increasing trend. (5) In the inlet of the North Passage, under the combined influence of decreased flow split and sediment split ratios, the decreased SSC in the basin and the sea area and decreased amount of resuspension, the SSC displayed a decreasing trend. In the middle section, because the increased amount caused by sediment going over the dyke was markedly more than the decreased amount caused by external environments, the SSC tended to increase. Holistically, the sharp decrease in sediment discharge caused synchronized SSC decreases in the Yangtze River Estuary. But there were still areas, where the SSC displayed increasing trends, indicating synchronicity and difference in the response of SSC to the sharp decrease in sediment discharge from the basin.     

长江上游干支流悬移质含沙量的变化及其原因

河流含沙量的变化是流域自然与人文因子变化的反映。以长江上游干支流1956~2000年的水沙和降水资料为基础,运用时间系列分析和统计分析方法进行研究。研究发现,干流宜昌站和4条主要支流含沙量的变化不是同步的,4条主要支流含沙量的变化呈现出复杂变化图形。流域面平均年降水量的变化,仅能解释含沙量变化的15.86%~37.21%,说明气候因素的变化不是长江干支流含沙量变化的主要原因。运用双累积曲线分析方法,研究了人类活动 (如水库修建,交通、矿山和城市建设,水土保持,植被破坏和恢复等 )对含沙量变化的影响。人类活动影响在不同的流域有较大差异。与4条主要支流相比,长江干流宜昌站含沙量的变化较小,反映了尺度效应的影响。多元回归分析表明,屏山 、高场、北碚、武隆4站的年均含沙量变化对宜昌站年均含沙量变化的贡献率分别为28.5%、12.6%、44.2%和14.7%。     

黄河入海泥沙悬移输送机制的控制试验(英文)

Five diagnostic experiments with a 3D baroclinic hydrodynamic and sediment transport model ECOMSED in couple with the third generation wave model SWAN and the Grant-Madsen bottom boundary layer model driven by the monthly sediment load of the Yellow River, were conducted to separately diagnose effects of different hydrodynamic factors on transport of suspended sediment discharged from the Yellow River in the Bohai Sea. Both transport and spatio-temporal distribution of suspended sediment concentration in the Bohai Sea were numerially simulated. It could be concluded that suspended sediment discharged from the Yellow River cannot be delivered in long distance under the condition of tidal current. Almost all of sediments from the Yellow River are deposited outside the delta under the condition of wind-driven current, and only very small of them are transported faraway. On the basis of wind forcing, sediments from the Yellow River are mainly transported north-northwestward, and others which are first delivered to the Laizhou Bay are continuously moved northward. An obvious 3D structure characteristic of sediment transport is produced in the wind-driven and tide-induced residual circulation condition. Transport patterns at all layers are generally consistent with circulation structure, but there is apparent deviation between the depth-averaged sediment flux and the circulation structure. The phase of temporal variation of sediment concentration is consistent with that of the bottom shear stress, both of which are proved to have a ten-day cycle in wave and current condition.     

Diagnostic experiments for transport mechanisms of suspended sediment discharged from the Yellow River in the Bohai Sea

Five diagnostic experiments with a 3D baroclinic hydrodynamic and sediment transport model ECOMSED in couple with the third generation wave model SWAN and the Grant–Madsen bottom boundary layer model driven by the monthly sediment load of the Yellow River, were conducted to separately diagnose effects of different hydrodynamic factors on transport of suspended sediment discharged from the Yellow River in the Bohai Sea. Both transport and spatio-temporal distribution of suspended sediment concentration in the Bohai Sea were numerially simulated. It could be concluded that suspended sediment discharged from the Yellow River cannot be delivered in long distance under the condition of tidal current. Almost all of sediments from the Yellow River are deposited outside the delta under the condition of wind-driven current, and only very small of them are transported faraway. On the basis of wind forcing, sediments from the Yellow River are mainly transported north-northwestward, and others which are first delivered to the Laizhou Bay are continuously moved northward. An obvious 3D structure characteristic of sediment transport is produced in the wind-driven and tide-induced residual circulation condition. Transport patterns at all layers are generally consistent with circulation structure, but there is apparent deviation between the depth-averaged sediment flux and the circulation structure. The phase of temporal variation of sediment concentration is consistent with that of the bottom shear stress, both of which are proved to have a ten-day cycle in wave and current condition.     

A model for the retrieval of suspended sediment concentrations in Taihu Lake from TM images

A study was conducted in the Taihu Lake with the aim of deriving a model for the retrieval of suspended sediment (SS) concentrations from Landsat TM images and in situ sampled data. The correlation between suspended sediment concentrations of lake and the reflectance obtained from the TM images is significant. By TM images and in situ sampled data in summer and winter, we obtained a comparative uniform model for the retrieval of suspended sediment concentrations in the Taihu Lake, that is lnSS = a*(R3/R1) + b, where lnSS is the natural logarithm of the suspended sediment concentration, R1 and R3 are the reflectance coincident with the 1st band and the 3rd band in TM images, a and b are the regression coefficients. Furthermore, we analysed the errors particularly to make sure the model is valid. The model is accurate to within 0.33(RMSE), suggesting that this model may be applicable to predict suspended sediment in the Taihu Lake from TM image throughout the year.