A study on retrieval algorithms in oceanic passive microwave remote sensing using 1.4 GHz and 10.7 GHz bands

To retrieve sea-surface salinity (SSS) from radiometer data at 1.4 GHz, auxiliary data of sea-surface temperature (SST), surface roughness and meteorological variables are needed. The authors study oceanic passive polarimetric microwave remote sensing using 1.4 GHz and 10.7 GHz bands. A set of algorithms are developed for 1.4 GHz and 10.7 GHz microwave polarimetric radiometer at 50° incidence angle to retrieve wind vector, as well as other geophysical parameters, such as SSS, SST, atmospheric volumes of water vapor and liquid water. Idealized retrievals are conducted using 2324 simulated brightness temperatures of full Stokes parameters at 1.4 GHz and 10.7 GHz. Results indicate that SSS, SST, sea-surface wind speed, direction, atmospheric volumes of water vapor and liquid water can be inversed at the same time. This suggests an alternative way for SSS remote sensing.     

北极海域海面风场和海浪遥感观测能力分析

卫星遥感是开展北极海域海面风场和海浪分布特征与变化规律研究的重要手段。本文基于在轨多源卫星遥感数据,从遥感观测空间覆盖、时间覆盖和多源卫星遥感数据融合等方面开展北极海域海面风场与海浪遥感观测能力分析,研究主要结果为:基于ASCAT和HY-2A散射计可实现北极海域海面风场遥感观测,通过多星联合观测可获取北极海域时空分辨率优于12 h和0.1°的海面风场遥感融合数据;基于HY-2A、CryoSat-2、SARAL和Sentinel-3高度计可实现北极海域海浪遥感观测,同样通过多星联合观测可获取北极海域时空分辨率优于1 d和0.25°的海浪有效波高遥感融合数据;基于2016年北极海面风场和海浪遥感融合数据,分析得出北极海域海面风场和海浪在2月处于极大值,然后逐渐减小,7月最小,随后开始逐渐增大。本研究表明,基于多源散射计和高度计遥感观测可实现北极海域海面风场和海浪的高时空分辨率遥感业务化监测。     

基于HY-2A微波散射计海面风场资料的台风风剖面信息提取研究

台风风剖面信息是直观反映与台风中心不同距离的各点与平均风速关系的曲线,它是确定各级台风风圈范围的重要基础。本文利用HY-2A微波散射计海面风场资料,结合Holland风场模型提出了一种新的台风风剖面信息提取方法,并选取2012–2017年期间16期典型台风进行应用。结果表明:34 kt与50 kt风圈半径的平均均方根误差为37.6 km与18.3 km,该方法具有较好的适用性和精度。本研究对于描述台风结构特征及潜在的破坏力和台风可能的影响范围具有一定的现实意义。     

Comparison of sea surface wind field measured by HY-2A scatterometer and WindSat in global oceans

In this study, we present a comprehensive comparison of the sea surface wind ?eld measured by scatterometer(Ku-band scatterometer) aboard the Chinese HY-2 A satellite and the full-polarimetric radiometer WindSat aboard the Coriolis satellite. The two datasets cover a four-year period from October2011 to September 2015 in the global oceans. For the sea surface wind speed, the statistical comparison indicates good agreement between the HY-2 A scatterometer and WindSat with a bias of nearly 0 m/s and a root mean square error(RMSE) of 1.13 m/s. For the sea surface wind direction, a bias of 1.41° and an RMSE of 20.39° were achieved after excluding the data collocated with opposing directions. Furthermore,discrepancies in sea surface wind speed measured by the two sensors in the global oceans were investigated.It is found that the larger dif ferences mainly appear in the westerlies in the both hemispheres. Both the bias and RMSE show latitude dependence, i.e., they have signi?cant latitudinal ?uctuations.     

A study of a new retrieval algorithm for measurement of oceanic windvectors field using satellite microwave scatterometer

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A study on remote sensing models of sea ice thickness by microwave radiometry

Extrapolating from the propagation theories of electromagnetic waves in a layered medium, a three-layer medium model is deduced in this paper by using microwave radiometric remote sensing technology which is suitable to first-year sea ice condition of the northern part of China seas. Comparison with in situ data indicates that for microwave wavelength of 10 cm, the coherent model gives a quite good fit result for the thickness of sea ice less than 20 cm, and the incoherent model also works well for thickness within 20 to 40 cm. Based on three theoretical models, the inversion soft ware from microwave remote sensing data for calculating the thickness of sea ice can be set up. The relative complex dielectrical constants of different types of sea ice in the Liaodong Gulf calculated by using these theoretical models and measurement data are given in this paper. The extent of their values is (0. 5-4. 0)-j(0. 07~0. 19).     

利用QuikSCAT/NCEP混合风场及WAVEWATCH模拟东中国海风浪场

将国际上比较成熟的海浪模式WAVEWATCH-Ⅲ移植到东中国海,采用QuikSCAT卫星遥感资料与NCEP数据混合风场作为强迫项,对该海区2000年1月23日至31日的一个大风天气过程下的风浪场进行了模拟计算。计算结果与浮标观测资料的对比结果说明,所获得的风浪场数值结果不但具有较高的时空分辨率,其精度也是比较高的。     

非对称风场对台风浪模拟效果的比较研究

分析四象限非对称风场模型与叠加风场模型的优缺点,将模型结果与实测风速进行对比验证;利用上述两种风场模型分别驱动第三代海浪模式SWAN,对发生在南海海域的三场台风浪进行了数值模拟计算。结果显示:四象限非对称模型关于风速的计算值与实测值吻合度更高,尤其是当台风中心距离测站较近时;四象限非对称模型驱动SWAN模拟的台风浪精度优于叠加风场模型,适用于南海台风浪的数值模拟。     

一种新的海洋风场反演中风向模糊排除方法研究

本文给出了一种从ＳＡＳＳ测量的后向散射强度手数据中反演出大尺度海洋风场的新方法。计算结果与Ｐｅｔｅｈｅｒｙｃｈ等利用ＳＡＳＳ表面风分析的结果比较在风向上是吻合的，在风速上本文所得结果更宇海面赵实风速。上述结果说明本文所采用的多解排除对两波束散射计探测海面风场的反演是成功的。     

基于GF-1卫星遥感影像的海岸线生态化监测与评价研究——以营口市为例

海岸线是海洋与陆地的分界线,也是重要的生态交错线。本文采用GF-1卫星遥感影像,通过监测大潮高潮时刻和小潮低潮时刻海岸水陆边界线,构建了潮间带完整性系数,以此为依据将海岸线划分为自然海岸线、具有基本生态功能的人工海岸线、具有部分生态功能的人工海岸线、具有有限生态功能的人工海岸线、具有少量生态功能的人工海岸线和无生态功能的人工海岸线。在此基础上,结合潮间带完整性系数及其毗邻海岸线长度,构建了海岸线生态化指数,用以评价区域海岸线的生态化程度。营口市海岸线以无生态功能的人工海岸线、自然海岸线和具有少量生态功能的人工海岸线为主,分别占到海岸线总长度的45.74%、18.31%和15.53%。营口市总体海岸线生态化指数为0.29,其中西城区、老边区、盖州北、鲅鱼圈区和盖州南分别为0.55、0.17、0.40、0.10和0.55。     

基于无人机多源遥感数据海岛植被叶面积指数协同反演研究

无人机多源遥感数据的获取、融合以及应用是当今研究的热点和难点。文中以城洲岛为例,针对海岛特殊的地理生态环境,获取无人机多源遥感数据。结合无人机多光谱遥感数据定量分析各遥感植被指数与植被叶面积指数(Leaf Area Index, LAI)的响应关系,构建单因子遥感反演模型;基于无人机激光LiDAR点云提取海岛植被冠层高度模型(Canopy Height Model,CHM),并将其作为自变量引入到多源统计回归分析中,从而构建多源遥感数据协同反演模型,对区域尺度下海岛叶面积指数(LAI)进行估算,开展验证和精度评价。结果显示,加入植被冠层高度因子的协同反演模型的判定系数R2为0.92,绝对平均误差系数为12.29%,预测精度要优于单因子反演模型(判定次数R2为0.86,绝对平均误差系数19.95%)。研究表明,加入了植被冠层高度因子的协同反演模型能在一定程度上提高乔木植被LAI的预测精度。实践证明,无人机多源遥感技术在生态学定量研究中具有巨大的潜力和广阔的应用前景。     

基于DINEOF方法重构台湾海峡叶绿素a遥感缺失数据的初步研究

卫星遥感观测是研究海洋环境变化的一种重要方法,但由于观测周期和天气影响等原因,观测数据经常存在一定的缺失,这使得遥感数据在海洋环境连续变化的应用研究中受到一定的限制.为解决此问题,本文采用了经验正交函数分解插值方法(DINEOF)重建缺失的遥感观测数据.首先,基于Sea Wi FS(1998年1月至2010年12月)、MODIS-Aqua(2002年7月至2014年12月)和MODIS-Terra(2000年2月至2014年12月)三级叶绿素a月平均数据产品,按像素点平均的方法组合成原始资料集;其次,利用DINEOF方法重构该资料集的缺失部分,从而得到完整的1998~2014年台湾海峡及邻近海域叶绿素a浓度的月平均数据集;再通过分析重构影像与原始资料的时空误差和验证重构影像的时空变化特征等方法,评价了所用算法和重构数据集的合理性.结果表明:基于遥感组合数据,采用DINEOF方法重构的叶绿素a遥感影像,能够有效地反映研究海域叶绿素a浓度的时空变化规律.研究还表明,该方法操作简便,无需先验信息,且重构精度高,能有效重构大面积缺失的影像数据资料,为探索海洋环境和生态的长期变化规律提供了较好的基础.     

海域使用格局卫星遥感监测与评价——以葫芦岛试验区为例

研究了海域使用类型遥感监测的分类系统,探索建立了各类海域使用类型的卫星遥感监测方法。在此基础上,以葫芦岛试验区为例,对该验区海域使用格局进行了卫星遥感监测与评价。结果表明:卫星遥感技术结合地理信息系统技术与全球定位系统技术可以较好地对海域使用空间格局进行监测和评价。葫芦岛试验区海域使用类型以工矿业用海和渔业用海为主,工矿业用海以大斑块的集中用海为主要特征,而渔业用海则以小斑块的分散用海为主。在海域使用空间格局上,葫芦岛区块海域以工矿业用海为主,兴城区块海域以工矿业和渔业用海为主,绥中区块海域则是以渔业用海为主,葫芦岛试验区海域使用空间格局具有明显的空间分异特征。     

GF-3号SAR卫星遥感围填海监测方法研究——以大连金州湾为例

依据不同围填海类型在高分三号(GF-3)合成孔径雷达(synthetic aperture radar,SAR)卫星遥感影像上可分性,建立围填海遥感分类体系及相应的围填海类型解译标志,进而分析SAR图像岸线提取方法,构建GF-3围填海监测技术流程。采用几何主动轮廓模型进行GF-3 SAR影像自动提取海岸线,获得围填海专题图。通过外业精度调查验证GF-3 SAR卫星遥感影像可以有效获取围填海信息。     

卷积神经网络在卫星遥感海冰图像分类中的应用探究

本文以TensorFlow为框架搭建卷积神经网络,基于迁移学习的思想,以经典的手写数字识别作为引入,对不同代价函数和激活函数组合对卷积神经网络模型分类结果影响进行了评价分析。以HJ-1A/B渤海海冰图像为实验数据源,分析了不同函数组合对遥感海冰图像分类的影响,优选出交叉熵代价函数与ReLU激活函数为最佳的组合,证明了卷积神经网络在遥感海冰分类中的应用可行性。对渤海海冰图像分类结果进行验证,其中带标签样本验证精度为98.4%。使用该模型对无标签的测试样本进行识别,讨论了样本的窗口尺寸对海冰分类结果的影响,发现在400×400小范围分类实验中最佳窗口尺寸为2×2;最后对整个渤海海域进行识别验证,效果较好。     

A study of SAR remote sensing of internal solitary waves in the north of the South China Sea:I.Simulation of internal tide transformation

For settlement of the well-known problem of contemporary radar imaging models,i.e.,the pmblem of a general underestimation of radar signatures of hydrodynamic features over oceanic internal waves and underwater bottom topography in tidal watels at at high radar frequency bands(X-band and C-band),the impact of the ocean surface mixed layer turbulence and the significance of strat-ified oceanic model on SAR remote sensing of internal solitary waves are proposed.In the north of the South China Sea by utilizing seme observed data of background field the nonlinearity coefficient,the dispersion coefficient,the horizontal variability coefficient and the phase speed in the generalized K-dV equation are determined approximately.Through simulations of internal tide transfor-mation the temporal evolution and spatial distribution of the vertical displacement and horizontal velocity of intereal wave field are obtained.The simulation results indicate that the maximum amplitudes of internal solitary waves occur at depth 35 m,but the maximum current speeds take place at depth 20 m in this area of the sea(about 20°30'N,114°E)in August.It was noticed that considering the effects of flood current and ebb current respectively is appropriate to investigate influence of the background shear flow on coefficients of the K-dV equation.The obtained results provide the possibility for the simulation of SAR signatures of inter-nal solitary waves under considering the impact of ocean surface mixed layer turbulence in the companion paper.     

基于高空间分辨率遥感影像的港口区集约利用监测与评估——以渤海5个典型港区为例

采用高空间分辨率卫星遥感影像,建立了面向对象的港口空间格局遥感监测技术流程,构建出码头指数、堆场指数、港池指数、深水岸线指数、港口效率指数,用来定量描述港口空间组成与使用效能.并选取营口鲅鱼圈港区、锦州港区、京唐港区、烟台龙口港区、烟台芝罘港区5个渤海典型港口为例,开展了实证研究.结果显示:渤海区域港口码头岸线与码头、堆场、港池的平均基本比例为1. 00∶6. 96∶51. 85∶66. 05,营口鲅鱼圈港区的堆场和港池、锦州港区的堆场以及京唐港区的码头、堆场和港池面积比例均已超过区域平均值.渤海地区5个典型港区都有较大的提升空间,营口鲅鱼圈港区、京唐港区、锦州港区、烟台芝罘港区和烟台龙口港区分别有8 722、9 587、5 940、6 909、8 795万t的吞吐量潜力可供挖掘.     

A study of SAR remote sensing of internal solitary waves in the north of the South China Sea: Ⅱ. Simulation of SAR signatures of internal solitary waves

A new model developed from the full-spectrum model of Lyzenga and Bennett （ 1988 ） is built up by us preliminarily through considering the impact of the ocean surface mixed layer turbulence on SAR remote sensing of internal solitary waves. In the partial differential equation of the action spectral density of the surface gravity-capillary waves the source function representing the contribution of the turbulence is added besides the usual source function representing the contribution of the wind. The source function is determined by applying the κ - ε model and adopting the Nasmyth spectrum of oceanic turbulence （ Nasmyth, 1970; Oakey, 1982; Fan, 2002） on the basis of the previous simulation results of internal tide transformation obtained in the companion paper （Fan et al. ,2008）. Either under relatively high wind speed, or under low wind speed, our model predicts significant large modulations of radar backscatter at all three bands （ L, C and X bands） for both VV and HH polarization. These results prove that considering the impact of ocean surface mixed layer turbulence on SAR remote sensing of internal solitary waves is reasonable and appropriate for settlement of the well-known problem of contemporary radar imaging models.     

Modification of SAR spectra associated with surface wind fields in the sea off the Kii Peninsula: A case study

Using surface wave parameters and a high-resolution surface wind field derived from Synthetic Aperture Radar (SAR) image mode data, we have investigated the spatial modification of SAR spectra. We found a surface wind front, formed by sheltering effect of the Kii Mountains, separating high and low wind-speed regions in a sea area of an European Remote-Sensing Satellite (ERS) SAR image off the Kii Peninsula. A swell system propagating westward dominates in the whole sea area covered by the SAR image. The wavelength retrieved from the SAR spectra in the sheltered (non-sheltered) region is longer (shorter). Since the distributions of surface wave parameters and surface wind speed are so well correlated, it can be considered that the SAR spectra are modified differently by the sheltered/non-sheltered surface winds. In order to examine the phenomena observed on the SAR image we have estimated the wind-wave SAR spectrum using the SAR surface winds, a wind-wave spectrum model and a SAR wave imaging model. We assume that the SAR spectrum related to the swell is homogeneous in the area imaged by SAR, and that the SAR spectrum of the wind-wave components causes the observed SAR spectra modification. Differences between the observed SAR spectra and the estimated SAR spectra in the sheltered and non-sheltered regions agree well with each other. In the present case, it can be concluded that the observed SAR spectra can be regarded as a linear combination of the wind-wave SAR spectra and the swell SAR spectra.     

A field experimental study on recolonization and succession of macrobenthic infauna in defaunated sediment contaminated with petroleum hydrocarbons

A field experiment was carried out in Hong Kong to study the patterns of recolonization and succession of subtidal macrobenthos in defaunated sediment contaminated with petroleum hydrocarbons and to determine the time required for benthic recovery from petroleum contamination. A total of 31 species was found and 83 animals/tray and 14 species/tray on an average were recorded after one month. Initial colonization was dominated by polychaetes in both abundance and species number (accounting for 69.1% and 64.5%, respectively). Abundance of macrobenthos came to a small crest (308 animals/tray) after three months, reached a sharp peak (1257 animals/tray) after six months, and then declined to a steady level. Abundance, species number and diversity in the petroleum-contaminated sediment were significantly lower than those in the control sediment in the early successional stages, indicating deleterious effects of petroleum hydrocarbons on recolonization and succession of macrobenthos. Petroleum hydrocarbons in sediment significantly altered species composition of macrobenthos in recolonization and succession. No significant differences in community parameters and species composition between the petroleum-contaminated and the control communities were found after 11 months, indicating that macrobenthic community had recovered from petroleum contamination.