近岸浑浊水体大气校正算法研究进展

大气校正问题是海洋光学遥感的关键技术问题之一。精确的大气校正是实现高精度水色信息反演的前提。I类水体的大气校正算法发展相对成熟,其假设近红外(NIR)波段离水辐亮度为零,从而将NIR波段的大气程辐射外推至可见光(VIS)波段求出离水辐亮度实现大气校正。但是,II类水体由于受到悬浮物(TSM)和黄色物质(CDOM)的影响,其大气校正相对复杂。文中概述了国内外近岸浑浊水体大气校正算法的研究现状及应用效果,总结了各种算法的特点、优势和局限性。文中还提出了浑浊水体大气校正研究需要解决的关键问题,并展望了该领域未来的发展趋势和方向。     

胶州湾水体悬浮物浓度遥感反演模式优化研究

为了及时、准确的了解胶州湾水域总悬浮物情况,采用2001—2015年水面实测数据,选取HJ-1、MERIS、LandsatTM/ETM+三个不同卫星数据,通过ENVI软件分析计算TM/ETM数据的多波段组合与总悬浮物浓度之间的相关关系,选取相关系数最大者分别构建多元函数回归模型,对胶州湾总悬浮物浓度进行了遥感定量反演研究。结果表明,估算因子三波段模型432算法与悬浮物浓度的相关性最好(R20.8),反演精度较高,以此建立了悬浮物浓度三波段半分析+生物光学遥感反演模型,检验值R~2均高于0.85,并通过F检验法和均方根误差(RMSE)分析,证明误差的敏感性差,该模型相关系数及稳定性好。因此,三波段模型在这三种反演模型中精度最好。     

多传感器水色卫星数据融合在提高观测数据质量中的作用

多传感器水色卫星融合对于提高水色数据时空覆盖率和可靠性具有重要的意义。利用MODIS、MERIS和VIIRS多传感器水色卫星融合数据与时空匹配的现场实测数据进行对比,分析了两种融合方法(平均法和基于最优化技术的光学融合算法)在提高观测数据质量中的作用。结果表明,与现场实测数据对比,MERIS传感器测量的平均绝对百分比误差(MAPE)为18.5%,MODIS传感器的MAPE为13.4%,VIIRS传感器的MAPE为18.2%,平均法融合产品的MAPE为12.8%,基于最优化技术的光学融合产品的MAPE为9.6%,说明两种融合算法都能降低测量误差,通过数据融合可以显著地提高数据质量,其中基于最优化技术的光学融合法性能更优。     

Landsat-8 OLI卫星数据的大气校正检验及其应用

本文检验了Vanhellemont和Ruddick算法在浑浊的海洋沿岸水体中的适用性。采用基于Vanhellemont和Ruddick算法对2013—2015年黄河口水体的landsat-8 OLI数据进行大气校正,该算法得到的OLI反射率与黄河口高光谱实测反射率较一致, R为0.95,在483 nm(蓝)、561 nm(绿)、655 nm(红)波段处平均相对误差为16.4%、17.3%和25.7%。MODIS和Landsat-8 OLI数据获取的悬浮物浓度之间一致性较好, R为0.85,平均相对误差为20.5%,表明该算法适用于黄河口水体。基于时间序列OLI数据,得到了悬浮物浓度时空分布特征。黄河口悬浮物浓度变化差异主要由风速和输沙量引起的,风速和输沙量对悬浮物浓度的影响存在一定的时间滞后现象。     

近岸水体异源遥感反射率产品的融合方法研究

数据融合能够综合利用多源遥感数据优势,获取高空间分辨率和高测量精度的遥感影像,这对于近岸水体生态环境监测和灾害预警均具有重要意义。但目前使用的数据融合方法多是针对内陆水体或大洋水体的,其在近岸水体的适用性仍需进一步评估,因而本文开展了近岸水体遥感数据融合方法对比研究。本文以高空间分辨率的Sentinel-2 MSI影像和中等空间分辨率的Sentinel-3 OLCI影像为数据源,分别开展了基于小波变换（WTBF）、生物光学模型（BOBF）和混合像元分解（IUBF）三种方法的数据融合实验,并在此基础上借助现场实测Rrs数据与融合影像对应点的平均相对误差MRE、均方根误差RMSE、偏差bias和平均梯度对各种方法的融合数据质量和区域适用性进行了评估。结果表明：（1）OLCI的Rrs数据精度高于MSI。其中MSI在443 nm、560 nm和665 nm三个波段的MRE、RMSE均高于OLCI,表明MSI的Rrs精度相对OLCI较低;目视效果和平均梯度表明MSI的清晰度高于OLCI;（2）BOBF是三种方法中融合效果最佳的算法。WTBF和BOBF生成融合影像在三个波段的MRE、RMSE优于MSI。综合MRE、RMSE和bias来看,BOBF和WTBF所生成的影像Rrs准确性高于MSI,而IUBF生成的融合影像的MRE、RMSE和bias相对WTBF和BOBF较高,准确性较差;目视评价和平均梯度表征WTBF和BOBF生成影像的清晰度与MSI相近,BOBF清晰度高于WTBF,IUBF生成影像清晰度相对于OLCI有所提高但未达到MSI水平;（3）在Rrs更低的烟台近岸海域,BOBF生成的融合影像清晰度与MSI相当且Rrs准确性相对于MSI更高,BOBF在该海域具有良好的适用性。     

珠江河口混浊高产水域叶绿素a浓度的遥感估算模型

近年来为提高混浊高产水体叶绿素a浓度的估算精度,Gitelson等提出了一种基于红与近红外3个波段遥感反射率的概念模型.文章基于2004年的实测数据,检验该概念模型在珠江河口水域的适用性,估算该概念模型以及它的特殊形式--两波段模型对应的光谱位置,在此基础上构建利用卫星数据提取珠江河口水域叶绿素a浓度的遥感估算模型.结果表明,珠江河口混浊高产水域叶绿素a浓度与三波段模型和两波段模型均有很强的线性相关性,相关系数分别达到0.91与0.88.构建的三波段模型和两波段模型估算的叶绿素a浓度与实测叶绿素a浓度的均方根差(RMSE)分别为5.82mg·m-3和6.53mg·m-3,精度高于其他常用算法.根据MERIS的波段设置构建的三波段模型估算的叶绿素a浓度与实测叶绿素a浓度的RMSE为6.47mg·m-3,显示了良好的应用潜力.     

基于SDGSAT-1影像的总悬浮物浓度反演方法研究

总悬浮物浓度是海洋的重要水质参数之一,其对水体透明度、水下光场及初级生产力有显著影响,同时对河流入海口与海岸带冲淤变化过程有重要作用。本文基于我国自主研制的SDGSAT-1卫星遥感影像,使用准分析算法（Quasi-Analytical Algorithm,QAA）获取水体固有光学量,并结合2022年4月黄河口区域总悬浮物浓度实测数据,建立水体固有光学量与总悬浮物浓度实测数据的单波段、波段加减、波段比值,以及多波段组合等模型并开展遥感反演,最后将反演结果同实测数据及基于Sentinel-2B影像的总悬浮物浓度反演结果进行对比。研究结果表明：基于SDGSAT-1影像的总悬浮物浓度反演结果在黄河口高浓度区域的决定系数为0.622,均方根误差为7.94 mg/L;基于Sentinel-2B影像的总悬浮物浓度反演结果在黄河口高浓度区域的决定系数为0.589,均方根误差为8.27 mg/L。故在我国近岸海域总悬浮物浓度反演方面,SDGSAT-1影像反演精度与Sentinel-2B影像反演精度相媲美。     

大气校正模型对多光谱水深反演影响的多维度分析

大气校正是水体定量遥感的基础与前提。本文从大气校正模型、大气校正模型参数、水体组分差异以及水深反演波段组合方式4个维度探讨大气校正模型对水深反演的影响。研究采用6S、FLAASH、ACOLITE与QUAC 4种大气校正模型,选取大陆型、海洋型与城市型气溶胶模式,以瓦胡岛西北侧与谢米亚岛周边浅水作为清洁水体研究区,以辽东浅滩与槟城海峡作为浑浊水体研究区,基于Landsat-8多光谱影像开展大气校正,并采用8种波段组合方式进行水深遥感反演。研究结果表明:（1）4种大气校正模型均可在一定程度上削弱大气对水体信号的影响;因参数选取以及研究区水体组分的不同,不同模型的校正结果存在一定差异;两类水体反射率峰值分别出现在蓝波段与绿波段;（2）6S大气校正模型鲁棒性较强,该模型因研究区水体组分发生变化导致对应的水深反演结果与其余模型相比波动较小;FLAASH模型在海洋型和城市型两种气溶胶模式水深反演结果在浑浊水体存在较为明显的差异,辽东浅滩浅水区平均相对误差相差7.9%;ACOLITE模型受水体类型影响显著且对浑浊水体具有优越性与稳定性,平均相对误差较FLAASH降低5.6%;（3）多波段水深反演精度普遍优于单波段,但反演精度与波段数目之间无显著的相关性;水深反演波段组合方式对不同研究区敏感性不同,清洁水体三波段模型的反演精度较好,浑浊水体中四波段模型的反演精度最优,平均相对误差较三波段模型降低达5.6%。     

黄、东海边界悬浮物输运量的卫星遥感估算

利用2002—2015年的中等分辨率成像光谱仪(Moderate Resolution Imaging Spectroradiometer, MODIS)第4波段反射率产品对黄、东海边界的悬浮物输运情况进行了分析, 同时利用黄、东海2003年现场实测的悬浮物含量数据和这期间准实时的MODIS影像数据, 建立了基于MODIS第4波段遥感反射率的悬浮物含量遥感反演模型。基于该模型, 反演黄、东海表层悬浮物浓度, 并计算悬浮物扩散面积。利用反演得到的表层悬浮物浓度和悬浮物浓度垂向预测模型, 获取垂直方向上的悬浮物浓度, 同时结合水深、扩散面积数据, 计算特定时刻水体中的悬浮物含量。利用插值方法获得整个输运过程中各时刻水体中的悬浮物的含量, 计算各个时刻悬浮物含量的总和作为悬浮物的输送量。对2002年10月至2003年4月黄海向东海的悬浮输送量进行估算, 估算结果为153Mt。     

南海岛礁遥感影像大气校正算法研究

针对目前传统大气辐射传输模型使用时难以确定气溶胶光学厚度的问题,提出一种仅依靠影像自身信息的大气校正算法,该算法针对南海水域清澈的特点,将暗像元法和大气辐射传输模型相结合,通过暗像元匹配和迭代运算确定气溶胶。实验结果表明:该算法与Sen2cor算法相比大气校正后的地物剖面光谱曲线基本一致,校正后影像能够反映出水深与蓝绿波段对数比值较好的相关性,具有较好的使用价值。     

Retrieval of total suspended matter from MODIS 250?m imagery in the Bohai Sea of China

Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua and Terra satellites have unique advantages for monitoring coastal waters, owing to their high spatial resolution (250?m), short revisit period (1–2?days), and freedom from cost. An empirical retrieval model for concentration of total suspended matter (TSM) has been developed based on a statistical analysis of field surveys of TSM and remote sensing reflectance (R _rs) in the Bohai Sea of China. A robust linear relationship was established between the equivalent remote sensing reflectance (converting ASD-measured R _rs by spectral response function) in the 620–670?nm band (band 1) of MODIS and the concentration of TSM (R ²?=?0.95; n?=?27; RMS?=?0.512) acquired in August and September 2008. The model was validated via in situ measurements in September 2009, resulting in a mean relative error of 12.9?%. Then, the corresponding MODIS products of monthly average concentration of TSM were produced from January to December 2009. The distribution characteristics of TSM in the Bohai Sea of China are closely related with the spatial pattern and seasonal variability. This study demonstrates that the moderately high resolution of MODIS 250?m data is available for monitoring the transport and fate of materials in relatively smaller bodies of water.     

中国东部海域浮游植物类群遥感反演研究

浮游植物类群遥感反演能够为全面认识浮游植物在海洋生态系统中的作用提供重要的数据资料.但由于复杂的水体光学特性,近海浮游植物类群遥感反演存在着巨大挑战.本研究以复杂光学二类水体—中国东部海域为研究区,通过使用3种建模方法,即波段组合法、基于奇异值分解的多元线性回归法、基于奇异值分解的XGBoost回归法,利用遥感反射率数...     

基于BP神经网络的公交动态行程时间预测方法研究

公交行程时间的精确预测对于提升公交吸引力具有重要意义。本文基于公交车到离站的历史数据,综合考虑时间周期、站点、站间距离、天气等多个因素,建立了基于BP神经网络的公交车静态行程时间预测模型,以该模型为基础,采用动态迭代的方法,叠加多个站间行程时间预测结果,进一步构建了面向连续站点的公交车动态行程时间预测模型,实现对跨越多个站点的公交行程时间预测。以青岛市125路公交为例对算法进行测试。在模型的横向对比实验中,本模型预测结果的绝对误差均在50 s以内,平均绝对误差百分比(MAPE)为11.74%,均方根误差(RMSE)为23.15,R2的确定系数为0.905 1,SVM的MAPE、RMSE、R2 误差指标分别为:12.38%、38.33、0.743 6,LR对应的误差指标分别为:12.50%、25.59、0.884 1;在静态模型与动态模型的对比实验中,动态模型预测结果的MAPE为11.75%,RMSE为23.15,静态模型对应误差指标分别为:11.63%、26.74。研究结果表明,基于BP神经网络的公交动态行程时间预测模型比传统的静态预测方法具有更高的预测精度。     

Surface suspended matter off the Rhone river mouth from visible satellite imagery

The quantification of surface Total Suspended Matter (TSM) off the Rhone river mouth is investigated using SPOT-XS and Landsat-TM images collected in November 1994. The method of satellite data calibration from in situ measurements is discussed. It is based on TSM concentration measurements through filtration of surface water samples and on radiometric data collected with a 256-channel spectroradiometer in the range 400–1100 nm. Empirical relationships between reflectance and TSM concentration are established by linear regression analysis of the data. These relationships are then applied to the image data corrected from atmospheric and surface effects. A good agreement, within a factor of less than two, was found on derived TSM concentration values as compared with sea truth data. The results for three different river flows are presented: a quasi-normal river discharge, a flood situation and an intermediate situation. The TSM corresponding concentration maps are presented and discussed.     

Quantification of the Total Suspended Matter Concentration around the Sea Breaking Zone from In Situ Measurements and Terra/Aster Data

Remote sensing techniques can be used to quantify the total suspended matter concentration (TSM). The main objective of this study is the quantification of the TSM concentration around the sea breaking zone for a particular area of the Portuguese coast, near Aveiro city. The methodology used was based on in situ measurements and on multispectral satellite image from TERRA/ASTER. In situ experimental techniques were used to determine a relationship between the TSM concentration and the seawater reflectance. Empirical relationships were established between TSM concentration and the equivalent reflectance values for TERRA/ASTER at visible and near infrared bands computed from the experimental data. The reflectance values had a very high correlation with the TSM concentration in the wavelength between 500 and 900 nm. The ASTER image was calibrated, atmospherically and geometric corrected. Equations of linear, polynomial, logarithmic, power and exponential models were applied. The best results were found with the linear and polynomial models, with a determination factor higher than 0.95. However, the differences in the TSM concentration calculated for the three bands indicate that we should not use the information of a single band to obtain the TSM concentration.     

Quantification of the Total Suspended Matter Concentration around the Sea Breaking Zone from In Situ Measurements and Terra/Aster Data

Remote sensing techniques can be used to quantify the total suspended matter concentration (TSM). The main objective of this study is the quantification of the TSM concentration around the sea breaking zone for a particular area of the Portuguese coast, near Aveiro city. The methodology used was based on in situ measurements and on multispectral satellite image from TERRA/ASTER. In situ experimental techniques were used to determine a relationship between the TSM concentration and the seawater reflectance. Empirical relationships were established between TSM concentration and the equivalent reflectance values for TERRA/ASTER at visible and near infrared bands computed from the experimental data. The reflectance values had a very high correlation with the TSM concentration in the wavelength between 500 and 900 nm. The ASTER image was calibrated, atmospherically and geometric corrected. Equations of linear, polynomial, logarithmic, power and exponential models were applied. The best results were found with the linear and polynomial models, with a determination factor higher than 0.95. However, the differences in the TSM concentration calculated for the three bands indicate that we should not use the information of a single band to obtain the TSM concentration.     

FY-3A/MERSI, ocean color algorithm, products and demonstrative applications

A medium resolution spectral imager (MERSI) on-board the first spacecraft of the second generation of China’s polar-orbit meteorological satellites FY-3A, is a MODIS-like sensor with 20 bands covering visible to thermal infrared spectral region. FY-3A/MERSI is capable of making continuous global observations, and ocean color application is one of its main targets. The objective is to provide information about the ocean color products of FY-3A/MERSI, including sensor calibration, ocean color algorithms, ocean color products validation and applications. Although there is a visible on-board calibration device, it cannot realize the on-board absolute radiometric calibration in the reflective solar bands. A multisite vicarious calibration method is developed, and used for monitoring the in-flight response change and providing post-launch calibration coefficients updating. FY-3A/MERSI ocean color products consist of the water-leaving reflectance retrieved from an atmospheric correction algorithm, a chlorophyll a concentration (CHL1) and a pigment concentration (PIG1) from global empirical models, the chlorophyll a concentration (CHL2), a total suspended mater concentration (TSM) and the absorption coefficient of CDOM and NAP (YS443) from China’s regional empirical models. The atmospheric correction algorithm based on lookup tables and ocean color components concentration estimation models are described. By comparison with in situ data, the FY-3A/MERSI ocean color products have been validated and preliminary results are presented. Some successful ocean color applications such as algae bloom monitoring and coastal suspended sediment variation have demonstrated the usefulness of FY-3A/MERSI ocean color products.     

我国海区SeaWiFS资料大气校正

利用光谱辐射传输理论，结合海上同步实测资料，开发出我国海区SeaWiFS资料大气校正模型。经卫星资料处理结果比对，本模型在一类水体，基本消除了412nm和443nm波段离水辐射率小于0的现象；在二类水体，利用临近一类水体的大气条件进行了有效的大气校正；同时建立了670nm,765nm,865nm波段的大气校正模型，这三个面适用于高浓度悬浮泥沙的信息提取。本模型用于处理我国海区的SeaWiFS资料比美国NASA模型更适合我国海区特定的大气和海洋环境，为SeaWiFS资料海洋水色信息提取和我国海洋一号（HY－1）及风云一号（FY－1C）卫星资料的大气校正研究提供了技术基础。     

全球海洋大气柱水汽含量遥感融合数据产品生成

本研究利用国际在轨SSMIS、WindSat、AMSR-E、ASMR2和国产HY-2A微波辐射计多源遥感大气柱水汽含量观测数据,基于最优插值算法,生成了2003－2015年的全球海洋每日0.25°高分辨率大气柱水汽含量多源遥感融合产品,以及2012－2015年未使用HY-2A微波辐射计数据的全球海洋每日0.25°遥感融合产品。利用无线电探空仪水汽含量观测数据,对生成的全部全球海洋大气柱水汽含量融合产品进行精度检验,结果表明,总体上,13年间均方根误差和标准差优于3 mm,平均偏差优于0.6 mm,平均绝对偏差优于2 mm,相关系数优于0.98;使用HY-2A微波辐射计数据产品会使融合结果的精度出现微小的降低;AMSR2和HY-2A微波辐射计数据的联合使用对于替代AMSR-E数据具有积极意义。     

Ocean color products retrieval and validation around China coast with MODIS

Waters along China coast are very turbid with high concentrations of suspended sediment nearly all the time,especially at the Hangzhou Bay,the Changjiang (Yangtze) River Estuary and the shoal along Jiangsu Province.In these turbid and optically complex waters,the standard MODIS ocean color products tend to have invalid values.Because the water-leaving radiances in the near-infrared (NIR) are significant resulting from the strong scattering of suspended particles,the standard MODIS atmospheric correction algorithm often gets no results or produces significant errors.And because of the complex water optical properties,the OC3 model used in the standard MODIS data processing tends to get extremely high chlorophyll-a (Chl-a) concentrations.In this paper,we present an atmospheric correction approach using MODIS short wave infrared (SWIR) bands based on the fact that water-leaving radiances are negligible in the SWIR region because of the extreme strong absorption of water even in turbid waters.A regional Chl-a concentration estimation model is also constructed for MODIS from in situ data.These algorithms are applied to MODIS Aqua data processing in the China coastal regions.In situ data collected in the Yellow Sea and the East China Sea in spring and autumn,2003 are used to validate the performance.Reasonably good results have been obtained.It is noted that water-leaving reflectance in the NIR bands are significant in waters along the China coast with high sediment loadings.The satellite derived and in-situ reflectance spectra can match in the turbid waters along China coast,and there is relatively good linear relationship between satellite derived and in-situ reflectance.The RMSE value of Rrs(λ) is 0.0031 sr ?1 for all the nine ocean color bands (412 to 869 nm).The satellite-derived Chl-a value is in the reasonable range and the root mean square percentage difference is 46.1%.