梳状高度计编队探测海洋涡旋仿真分析

单颗星下点高度计卫星可进行一维海面高度测量,但时空分辨率较低,对涡旋的探测能力不足。梳状高度计卫星编队可提升海面高度时空分辨率,增强对涡旋的识别探测能力。为定量分析高度计编队下的涡旋探测能力,本文在黑潮延伸体海域开展观测仿真实验,对海平面高度进行沿轨采样,经优化插值算法处理后得到逐天海面高度异常数据场并进行涡旋识别与统计分析。此外,本文还同步开展了单颗星下点高度计和成像高度计卫星涡旋探测仿真实验及对比分析。结果表明,梳状高度计卫星编队在涡旋数量、极性、半径及振幅等方面识别效果较好,与成像高度计探测结果相近。

人类活动对辽河口海岸线和海岸带景观演变影响

海岸线和海岸带景观对于维系河口海岸带生态系统稳定意义重大。利用遥感(remote sensing,RS)和地理信息系统(geographic information system,GIS)技术,获取辽河口海岸线1985-2017年Landsat遥感影像数据,对海岸线长度变化、岸线属性变化以及海岸带景观类型演变特征进行分析。结果表明:(1)1985-2017年辽河口海岸线呈淤积的趋势,海岸线总体向海迁移,海岸线类型由天然岸线向人工岸线转变。海岸线长度减少5.09 km,海岸线蜿蜒形态无明显变化。人类活动是辽河口海岸线迁移和转变的主要因素。(2)辽河口潮滩的边缘密度整体下降;道路的斑块密度总体PD上升0.15,最低值为0.01(1985);自然景观斑块所占面积比例逐渐下降,农田的PLAND值逐渐升高;人为景观的面积加权平均斑块分维数指数逐渐变小表明人类活动对辽河口海岸带景观的干扰逐渐变强。(3)1985-2017年间,泥滩和河流面积减少,养殖、城镇、水库、油井、农田、道路等用地面积增长7975.42 hm^(2),增长占比为11.37%。1994年出的现农田和水库岸线,且均由自然岸线转化而来。

北极海域海浪变化及归因分析

北极海浪是北极地区重要的海洋环境要素,为了进一步了解北极海域海浪变化及归因,本文通过利用海浪数值模式WAVEWATCH-Ⅲ(WW3)对1993-2021年期间北极海域海浪进行模拟,将WW3模拟的海浪结果与OSTM/Jason-2高度计数据时空匹配,对比结果显示:两者数据的相关性(COR)为0.93,均方根误差为0.63 m,模拟结果适用于北极海域海浪变化研究。结果表明:(1)由于冬季平均海表面风速值较夏季更大,无海冰区能产生更高的海浪,导致北极海域冬季海浪强度明显高于夏季。而夏季由于海冰分布减少和厚度小于1 m的冰层增多,无冰区海浪传播冲击薄冰区域引发海冰破碎,同时引发厚度较薄的海域海浪活动,以此使得海浪活动范围比冬季广。(2)北极海域海浪存在周期性变化,但在年平均尺度上海浪强度总体呈上升趋势。海冰的厚度及密集度分布与海浪变化相反,呈下降趋势。说明海冰的厚度和密集度数值越大在一定程度上会限制海浪活动,同时,北极海域海浪活动的主要动力源是海面风场。

1990–2020年中国广西海岸线遥感监测数据集

广西南临北部湾,是“一带一路”交汇的重要门户,拥有丰富的沿海港口资源、海洋生物资源、滨海旅游资源。对于海岸线位置变化和类型转换的遥感监测,可为海岸带的可持续发展和管理提供了宝贵的科学数据支持。本文采用1990–2020年5个时段的Landsat TM/OLI数据,对广西沿海地区进行海岸线提取研究。利用Arc GIS 10.2软件对海岸线的位置进行可视化解译,然后进一步将海岸线划分为人工和自然海岸线两个主要类别和生物质海岸线、砂质海岸线等6个二级类别。本数据集具有时间序列长、精度高、海岸线类型全面和聚焦2015年(可持续发展元年)前后海岸线变化趋势的特点,可用于海岸线时空分布特征和海陆格局演变的研究。

基于Landsat影像的广东省海岸线遥感提取和变化研究

以广东省海岸线为研究对象,采集2000、2005、2010和2015共4期Landsat系列卫星遥感影像,通过修复归一化差值水体指数(MNDWI)和人工目视解译相结合的方法,提取了广东省4个时期的海岸线,借助ArcGIS的空间叠加分析和统计工具,研究其15 a以来的动态演变特征,并分析海岸线变化原因。结果表明:①2000—2015年,广东省海岸线总体呈增长趋势,长度增加158.57 km,年均增速为10.57 km/a。海岸线变化最显著的时段为2005—2010年,其次为2010—2015年,变化最缓慢的为2000—2005年,其年均变化率依次为0.14%、0.40%和0.24%。②从空间上看,珠海、汕头、揭阳、东莞和中山在广东省沿海14市中海岸线增长幅度最为显著。③广东省海岸线变迁趋势以向海延伸为主,驱动因素主要表现为填海造陆、沿海工程建设和围垦养殖等人为活动。

Monitoring discharge from deep-sea mining ships via optical satellite observations

Deep-sea mining may disturb the water column environment,including the surface water and deep-sea,and these disturbances should be carefully treated.Remote sensing provides high-resolution and accurate long-term observations in the area around deep-sea mining.Discharge from mining ships can be identified within few days from satellite observations based on changes in reflectance.A pioneer twomonth experimental deep-sea mining cruise was conducted by The Metal Company in the eastern Pacific Ocean from September 15 to November 17,2022.A report from Greenpeace indicated incidents of surface discharge and leakage during this mining experiment.In this study,satellite observations captured a clear signal over the surface water from September 24 to October 28,indicating the location with discharged water from the mothership.The number of pixels where the potential discharged water was identified in the satellite imagery ranged from 4 to 13.The discharged water was transported by the combined effects of wind and currents,locating continuously to the downwind side of the mothership's mooring location.Remote sensing provides a timely and accurate monitoring system for tracking water discharge during deep-sea mining.

Experimental Study on the Variation of Optical Imaging Characteristics with Zenith Angle due to Internal Solitary Waves in Sunglint

Internal solitary waves(ISWs)change the roughness of the sea surface,thus producing dark and bright bands in optical images.However,reasons for changes in imaging characteristics with the solar zenith angle remain unclear.In this paper,the optical imaging pattern of ISWs in sunglint under different zenith angles of the light source is investigated by collecting optical images of ISWs through physical simulation.The experiment involves setting 10 zenith angles of the light source,which are divided into area a the optical images of ISWs in the three areas show dark-bright mode,single bright band,and bright-dark mode,which are consistent with those observed by optical remote sensing.In addition,this study analyzed the percentage of the dark and bright areas of the bands and the change in the relative gray difference and found changes in both areas under different zenith angles of the light source.The MODIS and ASAR images display a similar brightness-darkness distance of the same ISWs.Therefore,the relationship between the brightness-darkness distance and the characteristic half-width of ISWs is determined in accordance with the eKdV theory and the imaging mechanism of ISWs of the SAR image.Overall,the relationship between them in the experiment is almost consistent with the theoretical result.

An improved algorithm for retrieving thin sea ice thickness in the Arctic Ocean from SMOS and SMAP L-band radiometer data

The aim of this study was to develop an improved thin sea ice thickness(SIT)retrieval algorithm in the Arctic Ocean from the Soil Moisture Ocean Salinity and Soil Moisture Active Passive L-band radiometer data.This SIT retrieval algorithm was trained using the simulated SIT from the cumulative freezing degree days model during the freeze-up period over five carefully selected regions in the Beaufort,Chukchi,East Siberian,Laptev and Kara seas and utilized the microwave polarization ratio(PR)at incidence angle of 40°.The improvements of the proposed retrieval algorithm include the correction for the sea ice concentration impact,reliable reference SIT data over different representative regions of the Arctic Ocean and the utilization of microwave polarization ratio that is independent of ice temperature.The relationship between the SIT and PR was found to be almost stable across the five selected regions.The SIT retrievals were then compared to other two existing algorithms(i.e.,UH_SIT from the University of Hamburg and UB_SIT from the University of Bremen)and validated against independent SIT data obtained from moored upward looking sonars(ULS)and airborne electromagnetic(EM)induction sensors.The results suggest that the proposed algorithm could achieve comparable accuracies to UH_SIT and UB_SIT with root mean square error(RMSE)being about 0.20 m when validating using ULS SIT data and outperformed the UH_SIT and UB_SIT with RMSE being about 0.21 m when validatng using EM SIT data.The proposed algorithm can be used for thin sea ice thickness(<1.0 m)estimation in the Arctic Ocean and requires less auxiliary data in the SIT retrieval procedure which makes its implementation more practical.

An empirical method for joint inversion of wave and wind parameters based on SAR and wave spectrometer data

Synthetic aperture radar(SAR)and wave spectrometers,crucial in microwave remote sensing,play an essential role in monitoring sea surface wind and wave conditions.However,they face inherent limitations in observing sea surface phenomena.SAR systems,for instance,are hindered by an azimuth cut-off phenomenon in sea surface wind field observation.Wave spectrometers,while unaffected by the azimuth cutoff phenomenon,struggle with low azimuth resolution,impacting the capture of detailed wave and wind field data.This study utilizes SAR and surface wave investigation and monitoring(SWIM)data to initially extract key feature parameters,which are then prioritized using the extreme gradient boosting(XGBoost)algorithm.The research further addresses feature collinearity through a combined analysis of feature importance and correlation,leading to the development of an inversion model for wave and wind parameters based on XGBoost.A comparative analysis of this model with ERA5 reanalysis and buoy data for of significant wave height,mean wave period,wind direction,and wind speed reveals root mean square errors of 0.212 m,0.525 s,27.446°,and 1.092 m/s,compared to 0.314 m,0.888 s,27.698°,and 1.315 m/s from buoy data,respectively.These results demonstrate the model’s effective retrieval of wave and wind parameters.Finally,the model,incorporating altimeter and scatterometer data,is evaluated against SAR/SWIM single and dual payload inversion methods across different wind speeds.This comparison highlights the model’s superior inversion accuracy over other methods.

基于我国CMIP6模式的北极海冰厚度比较及评价

本文选取了第六次国际耦合模式比较计划(CMIP6)中的8个中国地球气候系统模式,将这些模式的北极海冰厚度与华盛顿大学的PIOMAS海冰厚度同化产品进行对比,评估了所选模式1980-2014年北极海冰厚度多年平均空间分布和长期趋势,并通过泰勒评分法对各模式的模拟能力进行了量化。结果表明,无论3月还是9月,所有模式均与PIOMAS存在差异,偏差位置主要集中在格陵兰岛北部、巴伦支海、白令海峡附近。模式均低估北极3月和9月海冰中心区域厚度,此外还普遍高估3月海冰边缘区厚度。其中空间分布与PIOMAS最为相近的模式为FIO-ESM-2-0,其次为FGOALS-f3-L模式。海冰厚度的长期趋势表明,海冰厚度整体呈下降趋势,并且9月的下降程度明显大于3月,与PIOMAS长期趋势空间分布最为相似的模式为NESM3。在此基础上,本文进一步对比了82°N以北3种大气再分析资料、1种卫星观测产品与8个CMIP6模式的辐射分量,再分析资料及模式间辐射分量有很大的差别,其中有两个模式的辐射存在明显的异常, FGOALS-f3-L模式3月上行短波辐射和CIESM模式9月上行短波辐射严重偏小,这可能是由于模式模拟存在误差。

Experimental study on the variation of optical remote sensing imaging characteristics of internal solitary waves with wind speed

Optical remote sensing has been widely used to study internal solitary waves(ISWs).Wind speed has an important effect on ISW imaging of optical remote sensing.The light and dark bands of ISWs cannot be observed by optical remote sensing when the wind is too strong.The relationship between the characteristics of ISWs bands in optical remote sensing images and the wind speed is still unclear.The influence of wind speeds on the characteristics of the ISWs bands is investigated based on the physical simulation experiments with the wind speeds of 1.6,3.1,3.5,3.8,and 3.9 m/s.The experimental results show that when the wind speed is 3.9 m/s,the ISWs bands cannot be observed in optical remote sensing images with the stratification of h_(1)∶h_(2)=7∶58,ρ_(1)∶ρ_(2)=1∶1.04.When the wind speeds are 3.1,3.5,and 3.8 m/s,which is lower than 3.9 m/s,the ISWs bands can be obtained in the simulated optical remote sensing image.The location of the band’s dark and light extremum and the band’s peak-to-peak spacing are almost not affected by wind speed.More-significant wind speeds can cause a greater gray difference of the light-dark bands.This provided a scientific basis for further understanding of ISW optical remote sensing imaging.

Retrieval of Antarctic sea ice freeboard and thickness from HY-2B satellite altimeter data

Antarctic sea ice is an important part of the Earth’s atmospheric system,and satellite remote sensing is an important technology for observing Antarctic sea ice.Whether Chinese Haiyang-2B(HY-2B)satellite altimeter data could be used to estimate sea ice freeboard and provide alternative Antarctic sea ice thickness information with a high precision and long time series,as other radar altimetry satellites can,needs further investigation.This paper proposed an algorithm to discriminate leads and then retrieve sea ice freeboard and thickness from HY-2B radar altimeter data.We first collected the Moderate-resolution Imaging Spectroradiometer ice surface temperature(IST)product from the National Aeronautics and Space Administration to extract leads from the Antarctic waters and verified their accuracy through Sentinel-1 Synthetic Aperture Radar images.Second,a surface classification decision tree was generated for HY-2B satellite altimeter measurements of the Antarctic waters to extract leads and calculate local sea surface heights.We then estimated the Antarctic sea ice freeboard and thickness based on local sea surface heights and the static equilibrium equation.Finally,the retrieved HY-2B Antarctic sea ice thickness was compared with the CryoSat-2 sea ice thickness and the Antarctic Sea Ice Processes and Climate(ASPeCt)ship-based observed sea ice thickness.The results indicate that our classification decision tree constructed for HY-2B satellite altimeter measurements was reasonable,and the root mean square error of the obtained sea ice thickness compared to the ship measurements was 0.62 m.The proposed sea ice thickness algorithm for the HY-2B radar satellite fills a gap in this application domain for the HY-series satellites and can be a complement to existing Antarctic sea ice thickness products;this algorithm could provide long-time-series and large-scale sea ice thickness data that contribute to research on global climate change.

An ensemble learning method to retrieve sea ice roughness from Sentinel-1 SAR images

Sea ice surface roughness(SIR)affects the energy transfer between the atmosphere and the ocean,and it is also an important indicator for sea ice characteristics.To obtain a small-scale SIR with high spatial resolution,a novel method is proposed to retrieve SIR from Sentinel-1 synthetic aperture radar(SAR)images,utilizing an ensemble learning method.Firstly,the two-dimensional continuous wavelet transform is applied to obtain the spatial information of sea ice,including the scale and direction of ice patterns.Secondly,a model is developed using the Adaboost Regression model to establish a relationship among SIR,radar backscatter and the spatial information of sea ice.The proposed method is validated by using the SIR retrieved from SAR images and comparing it to the measurements obtained by the Airborne Topographic Mapper(ATM)in the summer Beaufort Sea.The determination of coefficient,mean absolute error,root-mean-square error and mean absolute percentage error of the testing data are 0.91,1.71 cm,2.82 cm,and 36.37%,respectively,which are reasonable.Moreover,K-fold cross-validation and learning curves are analyzed,which also demonstrate the method’s applicability in retrieving SIR from SAR images.

Unveiling three-dimensional sea surface signatures caused by internal solitary waves:insights from the surface water ocean topography mission

Internal solitary waves(ISW),characterized by large amplitude and long propagation distance,are widespread in global oceans.While remote sensing images have played an essential role in studying ISWs,they mainly exploit two-dimensional image information.However,with the launch of the surface water ocean topography(SWOT)satellite on December 16,2022,a unique opportunity has emerged to capture wide-swath three-dimensional ISW-induced sea surface information.In this study,we examine ISWs in the Andaman Sea using data from the Ka-band Radar Interferometer(KaRIN),a crucial sensor onboard SWOT.KaRIN not only provides backscattering satellite images but also employs synthetic aperture interferometry techniques to retrieve wide-swath two-dimensional sea surface height measurements.Our observations in the Andaman Sea revealed the presence of ISWs characterized by dark-bright strips and surface elevation solitons.The surface soliton has an amplitude of 0.32 m,resulting in an estimation of ISW amplitude of approximately 60 m.In contrast to traditional two-dimensional satellite images or nadir-looking altimetry data,the SWOT mission’s capability to capture threedimensional sea surface information represents a significant advancement.This breakthrough holds substantial promise for ISW studies,particularly in the context of ISW amplitude inversion.

Synthesizing high-resolution satellite salinity data based on multi-fractal fusion

The spaceborne platform has unprecedently provided the global eddy-permitting(typically about 0.25°)products of sea surface salinity(SSS),however the existing SSS products can hardly resolve mesoscale motions due to the heavy noises therein and the over-smoothing in denoising processes.By means of the multi-fractal fusion(MFF),the high-resolution SSS product is synthesized with the template of sea surface temperature(SST).Two low-resolution SSS products and four SST products are considered as the source data and the templates respectively to determine the best combination.The fused products are validated by the in situ observations and intercompared via SSS maps,Singularity Exponent maps and wavenumber spectra.The results demonstrate that the MFF can perform a good work in mitigating the noises and improving the resolution.The combination of the climate change initiative SSS and the remote sensing system SST can produce the 0.1°denoised product whose global mean standard derivation of salinity against Argo is 0.21 and the feature resolution can reach 30−40 km.

中国海洋卫星遥感技术进展

新中国成立70年来,中国在海洋卫星遥感技术领域取得了丰硕成果。中国制定了长远的自主海洋卫星发展规划,构建了海洋水色、海洋动力环境和海洋监视监测三大系列的海洋卫星,逐步形成了以中国自主卫星为主导的海洋空间监测网,在中国海洋资源与环境监测、海洋防灾减灾、海洋安全管理等方面发挥了重要作用。本文回顾了中国在海洋水色、海洋微波(海洋动力环境)卫星遥感技术的发展历程,重点介绍了中国在海洋卫星遥感技术领域所取得的新成果,并对中国海洋卫星遥感技术的未来发展进行了展望。

赤潮相关因子的卫星遥感探测与赤潮预报的可行性探讨

讨论遥感探测赤潮相关因子的技术方法以及现阶段遥感观测手段的不足之处 ,认为赤潮的监测和预报须依靠多层次的海洋观测系统和多学科的综合研究才能实现 ,其中 ,多层次的海洋观测手段是关键 ,建立有效的海洋综合观测系统是预报赤潮的必要条件 (如正在建设中的珠江口、上海海洋立体观测示范技术系统 ) ,利用已有的综合技术实现赤潮的预报是完全可能的 .

卫星跟踪浮标和卫星遥感海面高度中的南海涡旋结构

选择 4个南海卫星跟踪Argos漂流浮标及同期的TOPEX/Poseidon卫星遥感海面高度资料 ,研究了南海海域涡旋的活动及空间结构。这 4个Argos漂流浮标的轨迹除了基本符合各季节海盆尺度环流趋势外 ,分别在菲律宾以西、越南外海、南海中部等海域呈现出中尺度旋转轨迹。这些中尺度涡旋现象在同期的TOPEX卫星遥感海面高度异常 (SSHA)分布中得到了准确的印证 ,并在诊断得到的地转流场中对应了一系列瞬变的中尺度涡旋活动。

胶州湾遥感研究Ⅱ.动力参数计算

应用从卫星遥感图像中提取的平均高潮线水域面积和水边线水域面积推算零米以下水域面积,以及结合潮位实测资料推算海湾纳潮量与沉积速率的方法,得出胶州湾现有(1988年)零米以下水域面积为257km^2、纳潮量为9.48×10~8m^3。这些数值比历史数据减小。胶州湾1963—1988年间的平均沉积速率为1.4cm/a,是1915—1963年间的2.7倍。文中还对湾口最大涨潮流速的推算方法进行了探索,应用于胶州湾得出最大涨潮流速为1.2m/s,也比历史数据有所减小。

机载激光雷达照射下的海面散射特性研究

针对现有计算机技术在计算海面的激光散射时,大面积的具有统计意义的海面可以直接使用统计参数和解析近似方法计算,使用数值计算方法则只能计算平方厘米级别面积的海面或耗时相当长,而对于机载激光雷达照射下的海面,也即小区域海面,其已无统计参数,本文使用面元分解模型和基尔霍夫近似方法,基于Elfouhaily海谱对海面建模并进行精细的剖分,仿真计算了海面的激光雷达后向散射系数。分析了后向散射系数随入射角、海面面积、观测方向与风向角度之间的变化规律,以及散射系数计算结果的不稳定性。该方法可以为进一步研究海面激光散射提供一定的理论依据。