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1.
利用C波段RADARSAT-2单极化SAR图像的方位向截断波长估计有效波高 总被引：1，自引：1，他引：0
This paper proposes two simple models, look-up table(LUT) model and empirical model, to directly retrieve significant wave height(Hs) using synthetic aperture radar(SAR) azimuth cutoff(λc). Both models aim at C-band VV, HH, VH, and HV single-polarization SAR images. The LUT model relates Hs to λc, while the empirical model relates Hs to both λc and SAR range-to-velocity(β). The LUT model coefficients are derived by simulation under different sea states and observation conditions, which depend on incidence angle(θ), wave direction(dw), and βbut are independent of polarization. The empirical model coefficients are obtained by fitting the collocated data,which only depend on polarization. To fit empirical model coefficients and validate the two models, C-band RADARSAT-2 fine quad-polarization(VV+HH+VH+HV) single-look complex(SLC) SAR images and collocated buoy data are collected. Retrieved Hs, using Yang model and the two models proposed in this paper from four kinds of polarization SAR data, are compared with buoy Hs. Results show that both LUT and empirical models have the capacity of retrieving Hs from C-band RADARSAT-2 co-polarization SAR data, while Yang model is not suitable for these kinds of SAR data. Moreover, the empirical model is also valid for cross-polarization SAR data showing clear ocean wave stripes. 相似文献
2.
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 总被引：1，自引：1，他引：0
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. 相似文献
3.
利用ALOS PALSAR全极化SAR内波图像,对比分析了SAR海洋内波在11种极化特征与后向散射系数(σ0) 图像中的可视性。在提取的SAR极化特征图像中,Lambda值的内波特征最为明显,极化熵和极化角次之。与σ0图像相比,Lambda值的内波可视性优于同极化的σ0图像;对于极化熵和极化角,沿距离向传播的内波可视性优于同极化的σ0图像,沿方位向传播的内波可视性略差于同极化的σ0图像,两者均优于交叉极化的σ0图像。HH/VV极化比、归一化圆极化系数和Bata值的内波特征较弱;HH/HV极化比、VV/VH极化比、Gamma值、Delta值和各向异性指数的内波图像均不清晰,无法识别内波。 相似文献
4.
《Oceanic Engineering, IEEE Journal of》2005,30(3):508-515
A methodology for retrieving high-resolution ocean surface wind fields from satellite-borne synthetic aperture radar (SAR) data is introduced and validated. The algorithms developed are suited for ocean SAR data, which were acquired at the C band of either vertical (VV) or horizontal (HH) polarization in transmission and reception. Wind directions are extracted from wind-induced streaks that are visible in SAR images of the ocean at horizontal scales greater than 200 m. These wind streaks are very well aligned with the mean surface wind direction. To extract the orientation of these streaks, two algorithms are introduced, which are applied either in the spatial or spectral domain. Ocean surface wind speeds are derived from the normalized radar cross section (NRCS) and image geometry of the calibrated SAR images, together with the local SAR-retrieved wind direction. Therefore, several C-band models (CMOD IFR2, CMOD4, and CMODS) are available, which were developed for VV polarization, and have to be extended for HH polarization. To compare the different algorithms and C-band models as well as demonstrate their applicability, SAR-retrieved wind fields are compared to numerical-model results considering advanced SAR (ASAR) data from Environmental Satellite (ENVISAT), a European satellite. 相似文献
5.
Atmospheric frontal gravity waves observed in satellite SAR images of the Bohai Sea and Huanghai Sea 总被引：1，自引：0，他引：1
LIU Shuming LI Ziwei YANG Xiaofeng Pichel William G YU Yang ZHENG Quanan LI Xiaofeng 《海洋学报(英文版)》2010,29(5):35-43
In the satellite synthetic aperture radar (SAR) images of the Bohai Sea and Huanghai Sea, the authors observe sea surface imprints of wave-like patterns with an average wavelength of 3.8 km. Comparing SAR observations with sea surface wind fields and surface weather maps, the authors find that the occurrence of the wave-like phenomena is associated with the passing of atmospheric front. The authors define the waves as atmospheric frontal gravity waves. The dynamical parameters of the wave packets are derived from statistics of 9 satellite SAR images obtained from 2002 to 2008. A two-dimensional linear physical wave model is used to analyze the generation mechanism of the waves. The atmospheric frontal wave induced wind variation across the frontal wave packet is compared with wind retrievals from the SAR images. The CMOD-5 (C-band scatterometer ocean geophysical model function) is used for SAR wind retrievals VV (transmitted vertical and received vertical) for ENVISAT and HH (transmitted horizontally and received horizontally) for RADARSAT-1. A reasonable agreement between the analytical solution and the SAR observation is reached. This new SAR frontal wave observation adds to the school of SAR observations of sea surface imprints of AGWs including island lee waves, coastal lee waves, and upstream Atmospheric Gravity Waves (AGW). 相似文献
6.
生物地貌学研究生物过程和地貌过程之间的双向交互作用,是一门新兴的交叉学科。早期的生物地貌学关注陆地生态系统,近期海岸带成为生物地貌学研究的热点地区,尤其是滨海湿地(如盐沼、红树林)成为研究生物地貌学过程和机理的重要区域。本文回顾了生物地貌学研究的概念、历史发展和方法,选取滨海湿地作为生物地貌学的主要研究对象,并就其研究方向、重要因素以及核心机制展开综述。最后对生物地貌学在海岸带生态系统修复工作中的应用进行梳理,分析了生物地貌学在红树林修复、滨海盐沼湿地修复和互花米草入侵防控上的应用展望。 相似文献
7.
María Fernanda Adame David Neil Sara F. Wright Catherine E. Lovelock 《Estuarine, Coastal and Shelf Science》2010
Coastal wetlands provide important ecological services to the coastal zone, one of which is sediment retention. In this study we investigated sediment retention across a range of geomorphological settings and across vegetation zones comprising coastal wetlands. We selected six coastal wetlands dominated by mangroves over a gradient from riverine to tidal settings in Southeast Queensland, Australia. Each site was comprised of three distinct vegetation communities distributed as parallel zones to the coast line: seaward fringe mangroves, landward scrub mangroves and saltmarsh/ cyanobacteria mat of the high intertidal zone. We measured suspended sediment retention and sedimentation rates. Additionally, in order to assess the origin of sediment transported and deposited in the mangroves, glomalin, a novel terrestrial soil carbon tracer, was used. Our results show a mean average sedimentation of 0.64 ± 0.01 mg cm−2 spring tide−1, which was variable within sites, regardless of geomorphological setting. However, geomorphological setting influenced spatial patterns of sediment deposition. Riverine mangroves had a more homogeneous distribution of sediments across the intertidal zone than tidal mangroves, where most sedimentation occurred in the fringe zone. Overall, the fringe zone retained the majority of sediment entering the coastal wetland during a tidal cycle with 0.90 ± 0.22 mg cm−2 spring tide−1, accounting for 52.5 ± 12.5% of the total sedimentation. The presence of glomalin in suspended sediments, and thus the relative importance of terrigenous sediment, was strongly influenced by geomorphological setting, with riverine mangroves receiving more glomalin in suspended solids than tidal mangroves. Glomalin was also differentially deposited within the vegetation zones at different geomorphological settings: primarily at the fringe zone of tidal mangroves and within the scrub zone of riverine mangroves. The differences we observed in the spatial distribution of sedimentation and the difference in the origin of the sediment deposited in riverine and tidal mangroves are likely to have an impact on ecological processes. 相似文献
8.
文章以福建省漳江口国家级红树林自然保护区为研究区, 提出了一种联合星载光学和合成孔径雷达(SAR)影像的红树林与互花米草分布的自动提取算法, 提取研究区内红树林和互花米草的空间分布。本研究选择2016年、2017年和2018年各一景低潮时的Sentinel-2 A光学影像数据, 获取植被和其他地物的光谱和纹理信息。算法首先基于归一化植被指数、增强型植被指数、地表水分指数以及数字高程模型的相关规则计算红树林和互花米草的潜在分布区; 通过随机森林分类算法区分红树林和互花米草, 2016年、2017年和2018年影像的分类总体精度和Kappa系数分别为98.53%和0.980、96.52%和0.952、98.71%和0.978, 分类效果良好; 使用当年所有Sentinel-1 A/B的SAR影像获得研究区的常年海水分布范围, 使用与海水交界的判据, 实现红树林、互花米草提取范围的优化。研究表明, 研究区2016年、2017年和2018年红树林总面积分别为56.85hm2、59.88hm2和58.61hm2, 互花米草总面积分别为109.23hm2、124.00hm2和142.39hm2, 与前人的研究成果在红树林和互花米草的空间分布和面积量级上有较好的一致性。 相似文献
9.
红树林(Mangroves)是生长在热带和亚热带海岸潮间带的木本植物群落。老鼠簕(Acanthus ilicifolius)是我国红树林林下灌丛的主要物种,是林下植被碳库的主要构成成分。本研究选取深圳福田红树林区的林下、林窗、林缘和光滩等不同生境下自然生长的老鼠簕植株,测定植株生物量和光合特性等相关指标。研究表明,林窗生境下的老鼠簕植株的光合能力、光合固碳速率和地上生物量累积均达到最大;林下生境最不利于老鼠簕植株固碳;光滩的老鼠簕植株具有较高的地下生物量累积,但由于其蒸腾速率高、水分利用率低下,其固碳较低。光照强度是决定不同生境老鼠簕植株固碳的关键因子。在未来我国红树林造林中,老鼠簕可作为林下植被构建,以提高红树林生物量总碳库,但最适宜老鼠簕固碳的光照约为40%~80%。本文研究结果将为红树林造林实践中的物种选择和林分构建提供理论参考。 相似文献
10.
以覆盖黄河口湿地区域的Radarsat-2 SAR全极化影像和Landsat-5 TM影像为例,将4种极化方式的SAR影像与TM影像分别进行融合,采用支持向量机对融合结果进行滨海湿地典型地物土地覆盖分类,并对分类结果进行比较评价,分析不同极化方式的SAR影像与TM影像融合结果在滨海湿地地区的分类能力。实验结果表明:采用与SAR影像融合的方法能够提高TM影像的分类精度,其中HV极化方式的SAR影像与TM影像的融合结果分类精度最高,最适用于滨海湿地土地覆盖分类研究。 相似文献
11.
北极多年冰在近几十年有明显的减少趋势,与北极海冰的厚度、体积和夏季最小海冰范围的减少密切相关。合成孔径雷达(synthetic aperture radar, SAR)具有全天时、全天候成像能力,基于SAR卫星影像的海冰分类对监测北极多年冰具有重要意义。基于深度学习U-Net模型,以SAR图像的双极化信息为模型输入,构建了像素级的海水、一年冰和多年冰多分类模型。与已有SAR图像海冰分类方法(支持向量机、随机森林和卷积神经网络)进行对比,基于双极化SAR图像的U-Net海冰分类模型的准确率、平均重叠度和Kappa系数,分别达到了90.73%、0.831和0.849,优于其他对比模型,分别提升了4.08%～19.04%, 0.063～0.321和0.111～0.335。此外,针对SAR图像水平-垂直极化(horizontal-vertical polarization, HV)有明显的条状热噪声和水平-水平极化(horizontal-horizontal polarization, HH)受入射角效应而亮度不均匀的特点,设计敏感性实验,研究HV噪声、入射角和灰度共生矩阵(gray leve... 相似文献
12.
国外海岸沙丘形成与演化的研究 总被引：13，自引：0，他引：13
董玉祥 《海洋地质与第四纪地质》2001,21(2):93-98
自20世纪80年代以来，国外对海岸沙丘的研究已从主要对其地貌形态的研究转向海岸海丘与海岸变迁尤其是全球变化关系的研究上，海岸沙丘形成与演化的研究倍受关注，进行了大量研究并取得了一定的研究成果。这里介绍了国外在海岸沙丘形成与演化研究方面的主要进展及其成果，并以此探讨了国内今后开展海岸沙丘形成与演化研究的主要方向与问题。 相似文献
13.
滨海湿地是介于陆地生态系统和水生生态系统之间的特殊生态系统，是珍贵的湿地资源，具有重要的生态系统功能。掌握滨海湿地的分布状况对于我国滨海湿地自然资源的保护和管理意义重大。文章基于2018—2019年“哨兵2号”卫星10 m分辨率多光谱影像，完成广东、广西和海南滨海湿地的遥感制图；对岩石海岸、砂石海滩、淤泥质海滩、潮间盐水沼泽、红树林、河口水域、河口三角洲/沙洲/沙岛、海岸性咸水湖、海岸性淡水湖、浅海水域共10个亚类建立解译标志，通过目视解译，对滨海湿地进行分类和统计。研究结果显示：广东、广西和海南滨海湿地面积共计1 377 140 hm2，各地滨海湿地面积与岸线长度基本呈正相关，海岸线越长，滨海湿地面积越大，各地典型滨海湿地的类型也不相同。 相似文献
14.
Richard A. Davis Jr. Kristin E. Yale John M. Pekala Megan V. Hamilton 《Marine Geology》2003,200(1-4):103-123
Although the morphology of the barrier-inlet system along the west-central Florida coast is quite complicated, the stratigraphy of these barriers is rather simple. The basal Holocene unit in most cores is an organic-rich, muddy sand that represents a vegetated, paralic marine, coastal environment similar to that which is north and south of the present barrier system. Above that unit is a muddy, bioturbated sand that displays a marine fauna at most locations but also contains Crassostrea virginica in a few places. These sediments accumulated in a low-energy marine setting that may or may not have been protected by a barrier island. Much of this facies also represents sediment that was delivered as washover deposits in an intertidal or subtidal setting and was subsequently bioturbated. The facies that can be attributed to a barrier island with some certainty are no more than 3000 years old, and on most islands, are much younger. These are the shelly sand and sorted sand facies. The shelly strata represent deposition in nearshore, beach, supratidal washover or intertidal spillover environments, and tidal inlet and tidal delta channels, whereas the sorted sand is typical of eolian deposition in dunes or the backbeach and some tidal delta elements. The presence of Holocene oyster beds offshore of a present barrier suggests that some of these islands formed significantly offshore and moved to their present position through washover. It is likely that most of these barriers initially formed through upward shoaling by waves. Although there is significant morphologic difference between the wave-dominated and mixed-energy, drumstick barrier islands, their stratigraphy is quite similar. The only significant difference is the presence of extensive progradation on at least part of the drumstick islands and a relatively high amount of former washover deposits on the wave-dominated type. 相似文献
15.
Xavier López-Medellín Alicia CastilloExequiel Ezcurra 《Ocean & Coastal Management》2011,54(4):318-329
Mangroves in Northwestern Mexico are vital to maintain coastal environments healthy, to provide nutrients for several food chains, and to supply valuable goods and services that sustain and improve human livelihoods. Many of these values offer a range of opportunities for economic development that attract workers, investors and developers. Recently, federal privatization policies have promoted an accelerated coastal development of this region to obtain large profits in short times, creating competing and overlapping interests to use coastal environments and control key resources. Such intense developments are modifying the ecological conditions of many coastal areas, threatening the provision of important ecosystem services to society. After years of centralized decisions, new paradigms are needed to achieve a coastal management that ensures long-term ecosystem maintenance, fair resource use and social equity. Recognizing the multiplicity of actors involved in coastal management and using a qualitative research methodology, we identified and explored the perspectives of different key stakeholders in the states of Baja California Sur and Sonora, Mexico, to better understand their views on mangroves use and management as well as the interaction among them. We discuss similarities and/or discrepancies found among stakeholders’ perceptions by describing their central ideas and identifying overlapping interests that may create conflicts when defining development and conservation programs or formulating policies. This information also intends to encourage further research on the social-ecological system of the coasts in Northwestern Mexico and to contribute to address coastal management issues in integrated ways that consider the social dimension through documenting stakeholders’ narratives in the future. 相似文献
16.
Macrofauna along the Sudanese Red Sea coast: potential effect of mangrove clearance on community and trophic structure 
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下载免费PDF全文 Mangroves along the Sudanese Red Sea coast are under constant anthropogenic pressure. To better understand the influence of mangrove clearance on the intertidal benthic community, we investigated the composition, biodiversity and standing stock of the macrofauna communities at high‐, mid‐ and low‐water levels in three contrasting habitats: a bare sand flat, a cleared mangrove and an intact mangrove. In addition, a community‐wide metric approach based on taxon‐specific carbon and nitrogen isotope values was used to compare the trophic structure between the three habitats. The habitats differed significantly in terms of macrofaunal standing stock, community composition and trophic structure. The high‐ and mid‐water levels of the intact mangroves showed a distinct macrofaunal community characterized by elevated densities and biomass, largely governed by higher decapod and gastropod abundances. Diversity was similar for cleared and intact mangroves, but much lower for the bare sand flat. Community‐wide metrics indicated highest trophic diversity and community niche breadth in the intact mangroves. Differences between the cleared and intact mangroves can be partly attributed to differences in sediment characteristics resulting from mangrove clearance. These results suggest a significant impact of mangrove clearance on the macrofaunal community and trophic structure. This study calls for further investigations and management actions to protect and restore these habitats, and ensure the survival of this ecologically valuable coastal ecosystem. 相似文献
17.
《African Journal of Marine Science》2013,35(3-4):617-624
The tidal basin of the Kosi Bay lagoonal-lacustrine complex is dominated by fish traps that line the intertidal and subtidal environments. These have been considered significant sediment sinks, responsible for transformation of parts of the system from subtidal and intertidal sand-flat settings to mangrove habitats. Mangrove progradation has been attributed to sediment retention within the trap structures. Fish-trap counts since 1942 indicate no significant increase in trap number prior to 1980, but thereafter trap numbers have increased exponentially. Historical GIS analysis indicates a linear growth rate of mangrove areas since 1942, a trend not mirrored in the numbers of fish traps. Modelling of mangrove progradation indicates lateral extension rates per annum much lower than global figures for choked systems elsewhere. Modelling of choking thresholds for the Kosi Bay system yields a minimum date of ～2500 AD. By including sea-level rise within the model, newly formed mangrove communities may either be drowned or remain in step with predicted sea-level rises within the next 150–200 years. The role of fish traps in the conversion of subtidal environments to sedimentary environments dominated by mangroves is negligible, and this shallowing would not be of concern in light of the short-term nature of managerial timescales. 相似文献
18.
Brazilian legislation defines coastal zone as a national patrimony – the geographic space of interaction of air, sea and land formed by the counties directly influenced, but not necessarily by those located in the coastline; also included are those distant until 50 km from the coastline, holding activities of great impact for the coastal zone or its ecosystems. The definition includes also the territorial sea of 12 nautical miles. Coastal management is conducted by a national plan legally enforced, complemented by states and counties plans, and a coastal ecologic-economic zoning limited to small portions of the coastal zone. A resolution of the “Environmental National Council” defines as “permanent preservation areas”, of very restricted use, coastal ecosystems as mangroves, sand dunes, and reproduction sites of wild fauna. One could expect that the Brazilian coast should be more protected and properly managed than other countries where a national management plan is lacking (Argentina) or where the guidelines exist but are not yet legally enforced (South Africa). Notwithstanding, we note today in Brazil an intensification of conflicts opposing small-scale vs. industrial fishermen; shrimp farming vs. mangrove crab harvesting; resorts installation vs. native communities; oil and gas activities vs. NGOs; and conflicts on environmental permit between federal and state governmental agencies. This paper evaluates the possible reasons for the failure of the complex legal suite available in Brazil and suggests that participatory management and concerted actions with relevant stakeholders are the key elements for the successful cases. 相似文献
19.
Shorebirds, as migratory aquatic birds and top predators in intertidal ecosystems, can be affected by global environmental changes and escalations in local impacts on coastal lagoons and estuarine trophic networks. Many shorebirds winter in North African Atlantic coastal sites, most likely because these locations provide constant and reliable food supplies with less energy costs in comparison with the wintering sites of northern Europe. Although more information is available for other important southern coastal sites (e.g. Saharan Atlantic coastal desert and Guinean mangroves coast), very little information is available for the North African Atlantic coast. Here, we focus on the impact of shorebird predation on benthic macroinvertebrates in a major wintering site in this area—Sidi Moussa coastal lagoon, Morocco—using an exclosure experiment. For most of the macroinvertebrate species there was no significant effect of the exclusion of shorebird predation. Overall, our results do not show evidence that predation by shorebirds influenced the overall standing biomass of the benthic community. This may indicate that the benthic productivity is high enough to provide constant and reliable food supplies for non-breeding shorebirds. 相似文献