Study of coexisting upstream solitary wave packet and downstream wakes induced by Diaoyu Dao and its affiliated islands detected by satellite sun glitter

Taking the advantage of sun glitter(SG) observed from high-resolution satellites Gaofen-1(GF-1) and Gaofen-6(GF-6), a new method named Shield and Vortex 1-2(SAV1-2) for extracting spatial texture information from sun glitter was established. Sea surface texture detail information around Diaoyu Dao and its affiliated islands was extracted using SAV1-2. Meanwhile, the dynamic characteristics of the water environment were analyzed by combining the water color, temperature and dynamic data. The resu...     

台风中降雨对中国高分3号合成孔径雷达观测信号的影响

Gaofen-3(GF-3), a Chinese civil synthetic aperture radar(SAR) at C-band, has operated since August 2016.Remarkably, several typhoons have been captured by GF-3 around the China Seas over its last two-year mission.In this study, six images acquired in Global Observation(GLO) and Wide ScanSAR(WSC) modes at verticalvertical(VV) polarization channel are discussed. This work focuses on investigating the observation of rainfall using GF-3 SAR. These images were collocated with winds from the European Centre for Medium-Range Weather Forecasts(ECMWF), significant wave height simulated from the WAVEWATCH-III(WW3) model, sea surface currents from climate forecast system version 2(CFSv2) of the National Centers for Environmental Prediction(NCEP) and rain rate data from the Tropical Rainfall Measuring Mission(TRMM) satellite. Sea surface roughness,was compared with the normalized radar cross section(NRCS) from SAR observations, and indicated a 0.8 correlation(COR). We analyzed the dependences of the difference between model-simulated NRCS and SARmeasured NRCS on the TRMM rain rate and WW3-simulated significant wave height. It was found that the effects of rain on SAR damps the radar signal at incidence angles ranging from 15° to 30°, while it enhances the radar signal at incidence angles ranging from 30° to 45° and incidence angles smaller than 10°. This behavior is consistent with previous studies and an algorithm for rain rate retrieval is anticipated for GF-3 SAR.     

利用一种改进的算法对中国高分三号同极化SAR图像反演的有效波高的验证

Chinese Gaofen-3(GF-3) is the first civilian satellite to carry C-band(5.3 GHz) synthetic aperture radar(SAR).During the period of August 2016 to December 2017, 1 523 GF-3 SAR images acquired in quad-polarization(vertical-vertical(VV), horizontal-horizontal(HH), vertical-horizontal(VH), and horizontal-vertical(HV)) mode were recorded, mostly around China's seas. In our previous study, the root mean square error(RMSE) of significant wave height(SWH) was found to be around 0.58 m when compared with retrieval results from a few GF-3 SAR images in co-polarization(VV and HH) with moored measurements by using an empirical algorithm CSAR_WAVE. We collected a number of sub-scenes from these 1 523 images in the co-polarization channel,which were collocated with wind and SWH data from the European Centre for Medium-Range Weather Forecasts(ECMWF) reanalysis field at a 0.125° grid. Through the collected dataset, an improved empirical wave retrieval algorithm for GF-3 SAR in co-polarization was tuned, herein denoted as CSAR_WAVE2. An additional 92 GF-3 SAR images were implemented in order to validate CSAR_WAVE2 against SWH from altimeter Jason-2, showing an about 0.52 m RMSE of SWH for co-polarization GF-3 SAR. Therefore, we conclude that the proposed empirical algorithm has a good performance for wave retrieval from GF-3 SAR images in co-polarization.     

海洋二号微波散射计极地海冰识别算法研究

An Antarctic sea ice identification algorithm on the HY-2A scatterometer(HSCAT) employs backscattering coefficient(σ0) and active polarization ratio(APR) for a preliminary sea ice identification.Then standard deviation(STD) filtering and space filtering are carried out.Finally,it is used to identify sea ice.A process uses a σ0,STD threshold and an APR as sea ice indicators.The sea ice identification results are verified using the sea ice distribution data of the ASMR2 released by the National Snow and Ice Data Center as a reference.The results show very good consistence of sea ice development trends,seasonal changes,area distribution,and sea ice edge distribution of the sea ice identification results obtained by this algorithm relative to the ASMR2 sea ice results.The accuracy of a sea ice coverage is 90.8% versus the ASMR2 sea ice results.This indicates that this algorithm is reliable.     

Arctic sea ice volume export through the Fram Strait from combined satellite and model data: 1979–2012

By combing satellite-derived ice motion and concentration with ice thickness fields from a popular model PIOMAS we obtain the estimates of ice volume flux passing the Fram Strait over the 1979–2012 period. Since current satellite and field observations for sea ice thickness are limited in time and space, the use of PIOMAS is expected to fill the gap by providing temporally continued ice thickness fields. Calculated monthly volume flux exhibits a prominent annual cycle with the peak record in March(roughly 145 km3/month) and the trough in August(10 km~3/month). Annual ice volume flux(1 132 km~3) is primarily attributable to winter(October through May) outflow(approximately 92%). Uncertainty in annual ice volume export is estimated to be 55 km~3(or 5.7%). Our results also verified the extremely large volume flux appearing between late 1980 s and mid-1990 s. Nevertheless, no clear trend was found in our volume flux results. Ice motion is the primary factor in the determination of behavior of volume flux. Ice thickness presented a general decline trend may partly enhance or weaken the volume flux trend. Ice concentration exerted the least influences on modulating trends and variability in volume flux. Moreover, the linkage between winter ice volume flux and three established Arctic atmospheric schemes were examined. Compared to NAO, the DA and EOF3 mechanism explains a larger part of variations of ice volume flux across the strait.     

A comparison of two global ocean-ice coupled models with different horizontal resolutions

A global eddy-permitting ocean-ice coupled model with a horizontal resolution of 0.25 by 0.25 is established on the basis of Modular Ocean Model version 4 (MOM4) and Sea Ice Simulator (SIS). Simulation results are compared with those of an intermediate resolution ocean-ice coupled model with a horizontal resolution of about 1 by 1 . The results show that the simulated ocean temperature, ocean current and sea ice concentration from the eddy-permitting model are better than those from the intermediate resolution model. However, both the two models have the common problem of ocean general circulation models (OGCMs) that the majority of the simulated summer sea surface temperature (SST) is too warm while the majority of the simulated subsurface summer temperature is too cold. Further numerical experiments show that this problem can be alleviated by incorporating the non-breaking surface wave-induced vertical mixing into the vertical mixing scheme for both eddy-permitting and intermediate resolution models.     

Recent satellite-derived sea ice volume flux through the Fram Strait: 2011–2015

The Fram Strait(FS) is the primary region of sea ice export from the Arctic Ocean and thus plays an important role in regulating the amount of sea ice and fresh water entering the North Atlantic seas. A 5 a(2011–2015) sea ice thickness record retrieved from Cryo Sat-2 observations is used to derive a sea ice volume flux via the FS. Over this period, a mean winter accumulative volume flux(WAVF) based on sea ice drift data derived from passivemicrowave measurements, which are provided by the National Snow and Ice Data Center(NSIDC) and the Institut Francais de Recherche pour d'Exploitation de la Mer(IFREMER), amounts to 1 029 km~3(NSIDC) and1 463 km~3(IFREMER), respectively. For this period, a mean monthly volume flux(area flux) difference between the estimates derived from the NSIDC and IFREMER drift data is –62 km~3 per month(–18×10~6 km~2 per month).Analysis reveals that this negative bias is mainly attributable to faster IFREMER drift speeds in comparison with slower NSIDC drift data. NSIDC-based sea ice volume flux estimates are compared with the results from the University of Bremen(UB), and the two products agree relatively well with a mean monthly bias of(5.7±45.9) km~3 per month for the period from January 2011 to August 2013. IFREMER-based volume flux is also in good agreement with previous results of the 1990 s. Compared with P1(1990/1991–1993/1994) and P2(2003/2004–2007/2008), the WAVF estimates indicate a decline of more than 600 km~3 in P3(2011/2012–2014/2015). Over the three periods, the variability and the decline in the sea ice volume flux are mainly attributable to sea ice motion changes, and second to sea ice thickness changes, and the least to sea ice concentration variations.     

利用2012年中国北极考察现场观测数据和卫星遥感资料评估海洋2号卫星扫描辐射计数据反演北极海冰密集度的研究

A retrieval algorithm of arctic sea ice concentration(SIC) based on the brightness temperature data of "HY-2" scanning microwave radiometer has been constructed. The tie points of the brightness temperature were selected based on the statistical analysis of a polarization gradient ratio and a spectral gradient ratio over open water(OW), first-year ice(FYI), and multiyear ice(MYI) in arctic. The thresholds from two weather filters were used to reduce atmospheric effects over the open ocean. SIC retrievals from the "HY-2" radiometer data for idealized OW, FYI, and MYI agreed well with theoretical values. The 2012 annual SIC was calculated and compared with two reference operational products from the National Snow and Ice Data Center(NSIDC) and the University of Bremen. The total ice-covered area yielded by the "HY-2" SIC was consistent with the results from the reference products. The assessment of SIC with the aerial photography from the fifth Chinese national arctic research expedition(CHINARE) and six synthetic aperture radar(SAR) images from the National Ice Service was carried out. The "HY-2" SIC product was 16% higher than the values derived from the aerial photography in the central arctic. The root-mean-square(RMS) values of SIC between "HY-2" and SAR were comparable with those between the reference products and SAR, varying from 8.57% to 12.34%. The "HY-2" SIC is a promising product that can be used for operational services.     

Predicting impacts of climate change on the biogeographic patterns of representative species richness in Prydz Bay-Amery Ice Shelf

The research on the biological ecology of the Prydz Bay-Amery Ice Shelf in East Antarctica is inadequate under the increasing threat from climate change, especially for Antarctic fish and krill. The Dynamic Bioclimatic Envelope Model(DBEM) has been widely used in predicting the variation of species distribution and abundance in ocean and land under climate change; it can quantify the spatiotemporal changes of multi population under different climate emission scenarios by identifying the environm...     

高分一号卫星影像海岸带区域定位精度评价

以覆盖黄河三角洲和连云港区域的两景高分一号卫星遥感影像1A级产品为例,利用现场采集的地面控制点和1∶50 000的DEM产品,开展了影像自主定位和正射校正实验,制作了控制点偏移矢量图,并对影像的定位精度进行了分析。结果表明:高分一号卫星影像具有较好的自主定位精度,黄河三角洲区域影像定位精度在27.8m左右,连云港区域影像定位精度在53.8m左右;在单控制点的情况下,影像的定位精度在3m左右,最大偏移量约为6m;在多控制点下正射校正,影像的定位精度为1m左右,最大偏移量为1个像元;对比控制点偏移矢量图,检查点较影像同名点的偏移方向与大小基本一致,表明高分一号卫星影像内部刚性较好。     

高分一号卫星海岸带影像质量评价

高分一号(GF-1)是我国自主研制的宽幅带高空间分辨率遥感卫星,为分析其在海岸带地区的应用潜力,本文采用主观和客观相结合的评价方法,并与SOPT-5卫星影像进行比对,开展GF-1影像的成像质量评价。主观评价结果表明:GF-1影像表现能力与SPOT-5影像相当,在某些地物特征表现上与SPOT-5比较一致。客观评价表明:GF-1影像的4种统计参数与SPOT-5影像比较接近且各有高低,GF-1影像各波段的灰度分布更分散,地物间的可分性更高;GF-1影像各波段的信噪比和波段间的独立性与SPOT-5比较,基本相同,整体看来,GF-1具有较高的成像质量,在海岸带地区具有一定的应用潜力。     

基于高分四号卫星的黄海绿潮漂移速度提取研究

静止轨道卫星高分四号（GF-4）具有高时间分辨率（20 s）和高空间分辨率（50 m）的独特优势。为了挖掘GF-4卫星在海洋灾害监测中的应用潜力,本文基于2016年6月25日1天4景的GF-4卫星影像,利用最大相关系数法（MCC）,开展了黄海绿潮漂移速度提取研究,分析了海面风场、潮汐等对绿潮漂移的影响。研究发现:（1）MCC方法可高精度自动追踪GF-4影像中绿潮的分钟级（8~9 min）位置变化,绿潮漂移速率和方向的相对偏差分别为11%和5%;当2景GF-4影像的成像时间间隔增大至小时级（如6 h）时,随着绿潮斑块形状的改变,MCC方法绿潮自动追踪的准确性下降。（2）绿潮在1天之中的漂移速率和方向可发生显著变化,当日上午9时黄海绿潮漂移速率均值为（0.36±0.13）m/s,方向以东南向为主,至15时,绿潮漂移速率显著增加至（0.69±0.12）m/s,方向变为东北偏北。（3）绿潮漂移速度与海面风速的相关系数为0.74,绿潮漂移方向为风向偏右;绿潮的向岸、离岸运动与相应时刻的涨、落潮具有较好的对应关系。GF-4卫星数据可为绿潮快速漂移的高精度监测提供数据支撑。     

基于高分一号卫星影像的珊瑚岛礁分类方法

在国内外学者对珊瑚岛礁分类体系的研究的基础上,提出了一种适用范围较广的分类体系,利用高分一号多光谱卫星数据,对西沙群岛华光礁和盘石屿进行了最小距离、马氏距离、最大似然、神经网络、支持向量机等基于像元的监督分类和使用面向对象分类,并对分类结果进行精度评估。两次实验结果表明,支持向量机和面向对象分类方法精度较高,且面向对象分类方法具有更好的目视效果,在一定程度上能满足当前珊瑚岛礁信息提取的需要。     

海岸水边线提取方法在GF-2卫星影像中的适应性研究

准确提取海岸水边线是海岸线变迁研究中必不可少的基本工作。本文以海南省陵水黎族自治县2016年的GF-2影像为数据源,在大气校正和正射校正等预处理的基础上,结合数学形态学处理等方法,采用NDWI (Normalized Difference Water Index)阈值法、ISOADTA (Iterative Self-Organizing Data Analysis Technique Algorithm)、SVM (Support Vector Machine)和面向对象法（Object-Oriented Classification,OOC）等4种不同方法来对海岸水边线进行提取,并对其提取结果进行定性和定量评估,进而分析比较了这4种方法在提取人工海岸、砂质海岸和基岩海岸等3种不同海岸类型的水边线时的提取效果和提取精度。结果表明,SVM方法在3种海岸水边线上的总体提取效果最好,总体提取精度最高。     

高分二号卫星滨海湿地影像质量评价

以黄河口典型滨海湿地为实验区,采用主客观评价相结合的方法,在与SPOT-6卫星影像对比的基础上进行了GF-2卫星全色影像、多光谱影像以及融合影像的质量评价。目视主观评价表明,GF-2影像在滨海湿地地区整体表现能力上与SPOT-6影像相近,地物边界、纹理等细节信息方面优于SPOT-6影像;基于统计指标的客观评价结果显示,GF-2影像受噪声干扰的程度小于SPOT-6影像,承载的信息量与SPOT-6影像接近,多光谱影像以及融合影像各波段间的独立性也与SPOT-6影像相当,但在灰度、离散程度和地物可分性上与SPOT-6影像还存在一定的差距。     

高分六号遥感影像水深反演能力评价

水深是重要的海洋要素,水深遥感反演是获取浅水水深的重要手段。当前水深遥感反 演应用以国外卫星数据为主,国产卫星数据的研究和应用较少。本文针对国产高分六号卫星 （GF-6） 数据,以三亚南山港为研究区域,分别建立单波段回归模型、双波段比值模型、多波段 回归模型,进行多光谱影像的水深反演能力研究,并与国外主流哨兵2 号卫星（Sentinel-2） 数 据进行实验比较。实验结果表明：GF-6 遥感影像具有较好的浅水水深反演能力和一定的反演精度,各波段水深探测能力依次为：绿波段跃蓝波段跃红波段跃近红外波段,反演方法效果依次为：多波段模型跃双波段模型跃单波段模型。相较于Sentinel-2 数据,GF-6 数据水深反演精度与其一致,这表明GF-6 影像具备替代国外遥感数据进行水深反演的能力和大规模应用的潜力。本文针对GF-6 影像水深反演能力的研究方法和分析,结果将为国产高分系列卫星数据的水深反演研究和应用提供有益的参考。     

基于GF-4卫星的杭州湾悬浮泥沙浓度遥感监测研究

悬浮泥沙作为重要水质参数,其分布和动态变化对河口及近岸的生态、环境、物质循环等都具有深远的影响。我国静止轨道高分四号(GF-4)卫星数据具有高时间和高空间分辨率的观测优势,在水色遥感上具有重大应用潜力。为探究GF-4卫星对悬浮泥沙浓度的监测能力,本文以杭州湾为研究区,构建反演模型,利用静止海洋水色成像仪进行交叉验证。结果表明,以GF-4卫星第5和第4波段遥感反射率的比值作为遥感因子建立的反演模型精度较高,决定系数为0.92,均方根误差为223.2 mg/L,平均相对误差为17.2%。交叉验证结果显示,GF-4卫星作为一种新的遥感数据源,在低浓度区与静止海洋水色成像仪反演悬浮泥沙浓度分布相似,但在高浓度区的差异随浓度增高而增大,总体可满足中国大部分海区的监测需求。     

光谱信息与纹理特征结合的GF-1海上溢油检测研究

围绕溢油光学探测工作中油膜信息提取精度低等主要问题,本文利用10景GF-1 WFI数据,发展了一种以光谱信息与多种纹理特征相结合的油膜检测方法。该方法不仅充分考虑了不同光谱组合对油膜与海水的区分能力,并且在纹理特征选择中尝试并确定了灰度共生矩阵的窗口大小、方向、位移量和灰度量化级四个参数,结合不同情况的油膜选择了合适的纹理特征;最后,将选取的若干纹理特征量与最优光谱组合构成多波段数据,应用在4种监督学习分类器中,评价分析了油膜检测的准确性,最终确定支持向量机为最优分类器,这一结论将为今后的海上溢油监测工作提供参考。     

Landsat-8 与GF-1 卫星渤海海冰探测能力对比研究

为更有效地利用Landsat-8和GF-1卫星进行渤海海冰监测,从海冰检测和海冰类型识别两方面,开展Landsat-8与GF-1卫星的渤海海冰探测能力对比分析研究。实验研究表明,在海冰检测方面,GF-1区分海冰与海水的能力强于Landsat-8;在海冰类型识别方面,Landsat-8识别海冰类型的能力要强于GF-1影像。初步讨论了综合利用Landsat-8与GF-1卫星监测渤海海冰的方案。