基于DIEOF方法重构海表叶绿素a遥感缺失数据

以2007年1月到2010年12月的MODIS Aqua CHL-a Level 2海表水色产品为基础数据,获得南海北部海域海表叶绿素a浓度的月平均影像集,基于影像集数据的时空相关性利用DIEOF(Data Interpolating Empirical Orthogonal Functions)方法重构其缺失数据。通过分析重构前后数据变化、验证重构结果的时空特征、计算模型精度指标等对重构结果进行评价。研究结果表明:DIEOF方法重构的MODIS海表叶绿素a影像,能够体现研究区海表叶绿素a的时空变化特征,重构结果的复相关系数R2可达到0.98,平均绝对误差MAE小于0.01;该方法重构过程中无需先验信息,易操作,能够有效重构大面积成片缺失或缺失比例较高的影像。     

南海北部海域叶绿素a浓度时空特征遥感分析

利用2007-2010年MODIS的L2级叶绿素a浓度产品作为数据基础, 对叶绿素a浓度年平均和月平均数据进行分级分区处理, 研究南海北部海域叶绿素a浓度时空分布特征及其与海洋环境因素的关系。初步研究结果表明:2007-2010年在南海北部海域叶绿素a浓度的高值区(>5.0 mg/m3)主要分布在广东省沿岸河流的入海口, 分布范围在夏季最大, 在春秋次之, 在冬季最小;叶绿素a浓度的次高值区(1.0～5.0 mg/m3)主要分布在海岸线到50 m等深线之间的海域, 分布范围夏冬较大, 能扩展到50 m等深线附近, 而春秋较小, 会退缩到50 m等深线以内;叶绿素a浓度的中值区(0.3～1.0 mg/m3)主要分布在50 m到100 m等深线之间的海域, 时空变化复杂;叶绿素a浓度的低值区(<0.3 mg/m3)主要分布在100 m等深线以外的海域, 其区域平均值夏季最低, 春秋次之, 冬季最高, 同时该区域叶绿素a浓度在春夏秋三季空间分布较均匀, 而冬季受季风和黑潮入侵影响空间分布较为复杂。南海北部海域海表叶绿素a浓度的时空变化特征与季风、沿岸河流、海流、海表温度等海洋环境因素的变化有关。     

基于船舶走航拖曳观测的卫星遥感产品检验

利用船载多参数拖曳式剖面测量系统走航观测获取的台湾岛东南海域叶绿素a浓度连续剖面数据,开展了卫星遥感产品精度检验研究。研究表明,由MERIS反演的叶绿素a浓度产品的平均相对误差优于30%,拖曳剖面观测可为卫星遥感产品检验提供高质量的现场观测数据,而且与船舶、浮标及其他固定平台等传统定点观测方式相比具有明显的效率优势。     

南海北部水体叶绿素a浓度反演的生物光学模型

利用2003年至2005年秋季在南海多个航次的现场观测数据,研究了南海北部海区遥感反射率的变化,并分析了用于全球海洋叶绿素a浓度反演的OC2和OC4模型在本海区的适用性。结果表明,在南海北部海域,OC2和OC4模型高估了叶绿素a浓度,高估范围一般约在80%—200%之间,其中最高可达640%,即OC2和OC4模型并不适用于南海海域。在此基础上,根据现场实测的表观光学数据,利用遥感反射率比值(Rrs(433)/Rrs(555))与叶绿素a浓度的关系建立了两套能够精确反演南海北部海域叶绿素a浓度的本地化经验算法———算法1和算法2,并利用其对南海北部海域的叶绿素a浓度进行反演。结果表明,由本地化模型反演得到的叶绿素a浓度与实测的叶绿素a浓度具有较好的相关关系,其平均相对偏差分别为51%和53%,相关系数为0.75。     

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DINEOF的静止海洋水色卫星数据重构方法研究

静止轨道海洋水色成像仪(Geostationary Ocean Color Imager, GOCI)提供了时间分辨率达小时级的海洋水色数据,使得对海洋环境的逐时变化监测成为可能。然而受到海洋上空云、雾和霾的影响,数据出现连续高缺失率甚至完全缺失的情况,使得数据使用价值大大降低。在经验正交函数重构法(Data INterpolating Empirical Orthogonal Functions, DINEOF)的基础上,突出时间要素在重构中的地位,运用异常像元检测、拉普拉斯平滑滤波和时间模态2次分解插值,提出了适用于静止海洋水色卫星数据的重构方法——DINEOF-G。利用此方法对杭州湾2017年的GOCI总悬浮物质量浓度数据进行重构,结果表明该方法相比经典方法在重构精度上提高了8%,数据重构率提高了36%,且重构结果较好地反映了杭州湾总悬浮物质量浓度的季节变化规律和空间分布特征。     

南海叶绿素浓度季节变化及空间分布特征研究

以南海海域1997年10月至2002年9月SeaWiFS卫星遥感叶绿素浓度的资料为基础,分析了多年平均的南海叶绿素浓度的时空分布,初步分析结果表明,冬季南海大部分海域叶绿素浓度普遍较高,春季大部分海域较低;南海各个海区的叶绿素月平均最低浓度基本出现在春季的4月或5月,而最高浓度出现的月份却有不同的特征,在中央海盆区出现在12月,在广东沿岸海区出现在7月,在越南东南部近岸海域在8月和12月有两个最高值;在吕宋海峡的西部区域,尽管叶绿素浓度的最高值也出现在12月,但是叶绿素浓度的最低值却出现在夏季的7月.在空间上近岸区域的叶绿素浓度明显高于中央海盆区,西部海域普遍高于东部海域.南海叶绿素浓度的这一时空分布特征与流场(如上升流等)、海面温度场和风场等的变化有关,也与陆源物质的输入等关系密切.     

基于长时序遥感影像的胶州湾秋季叶绿素a浓度变化及其影响因素研究

水体中叶绿素a的含量是研究浮游植物生物量、初级生产力的重要指标，因此对于河口海湾区域叶绿素a的长期监测具有重要的生态学意义。借助遥感技术能够获取长时序大范围观测数据的特点，本文利用1986-2015年的Landsat TM/ETM+影像，通过构建基于实测数据的定量反演模型，得到了30年来胶州湾海域秋季叶绿素a浓度的分布情况:叶绿素a浓度的空间分布规律稳定，呈现西北高东南低的特点，叶绿素a浓度均值呈波动略有上升的趋势。本文利用遥感反演的胶州湾海表面温度及胶州湾流域的土地利用分类和景观格局指数，从自然因素和人为因素两方面对胶州湾叶绿素a浓度时空分布的影响因素进行分析，发现胶州湾秋季叶绿素a浓度与海表面温度密切相关，并且受到近海养殖区破碎化程度、修建大型人工设施等人为因素的影响。     

南海北部表层颗粒有机碳的季节和年际变化遥感分析

海洋颗粒有机碳（POC）是海洋固碳的一个关键参数。为了研究南海北部陆架及海盆表层POC浓度的时空分布特征以及变化趋势,本文利用2009-2011年4个季节的实测数据,对NASA发布的MODIS/AQUA卫星月平均POC遥感产品,进行了验证和校正;并利用校正后的遥感数据分析了2003-2014年POC的时空分布特征和变化趋势。发现POC遥感产品与南海北部实测数据具有较好的线性关系（R2=0.72）,但存在系统性偏高,需利用实测数据对遥感数据进行区域性校正。分析校正后的遥感数据发现,南海北部陆架POC浓度较高,平均为（33.34±8.02）mg/m3;吕宋海峡西南海域浓度较低,平均为（29.25±6.20）mg/m3;中央海盆区浓度最低,平均为（27.02±4.84）mg/m3。春夏季POC浓度较低,最低值一般出现在5月,冬季（12月至翌年1月）POC浓度达到最高。利用2003-2014年的长时间序列遥感叶绿素（Chl a）和海表温度（SST）、混合层深度（MLD）模式数据,以及实测数据对南海北部POC浓度的影响机制进行了分析。发现POC与Chl a在秋冬呈现较好的相关关系（R2=0.51）,但在春夏季较离散,表明秋冬季生物作用对POC影响较大。2003-2014年期间,POC与Chl a、MLD及SST存在明显的年际变化,但并没有显著的上升或下降趋势。     

基于DINEOF的风云极轨气象卫星海表温度重构方法研究

海表温度是表征海洋表层热力状况的重要海洋参数,日均全天候覆盖的海温观测数据可为服务台风监测及其他海洋灾害时空演变的精细化预报提供数据支撑。可见光红外扫描辐射计和中分辨率光谱成像仪反演的海温产品具有较高的空间分辨率,但是红外遥感反演的海温产品受到云、雾和霾的影响,在云下存在大面积、无规律的缺值;微波辐射计反演的海温产品空间分辨率低,但可穿透云层,实现全天候海温观测。本文基于风云三号B、C、D三颗极轨气象卫星红外和微波遥感仪器反演的海温资料,利用经验正交函数插值法(DINEOF)重构得到全球海表温度产品。与全球分析场日平均海温OISST数据进行比较可知：原始海温资料的均方根误差为0.59~0.70℃,DINEOF重构后海温资料均方根误差降至0.10~0.34℃;相关系数从0.33~0.48提升到0.78~0.98。多传感器重构海温数据空间分布上连续可信,能够监测不同季节的海温变化特征及暖池空间模态。风云三号气象卫星微波遥感的加入显著提升了重构海温的空间连续覆盖率和时间分辨率。     

Assessing the Validity of Seismo-Acoustic Predictor Equations for Obtaining Seabed and Sub-Surface Sediment Physical Properties

The interdependence between the seismo-acoustic properties of a marine sediment and its geotechnical/physical parameters has been known for many years, and it has been postulated that this should allow the extraction of geotechnical information from seismic data. Though in the literature many correlations have been published for the surficial layer, there is a lack of information for greater sediment depths. In this article, a desktop study on a synthetic seafloor model illustrates how the application of published near-surface prediction equations to subsurface sediments (up to several tens of meters burial depth) can lead to spurious predictions. To test this further, acoustic and geotechnical properties were measured on a number of sediment core samples, some of which were subjected to loading in acoustically-equipped consolidation cells (oedometers) to simulate greater burial depth conditions. For low effective pressures (representing small burial depths extending to around 10 meters subsurface), the general applicability of established relationships was confirmed: the prediction of porosity, bulk density, and mean grain size from acoustic velocity and impedance appears generally possible for the investigated sedimentary environments. As effective pressure increases through, the observed relationships deviate more and more from the established ones for the near-surface area. For the samples tested in this study, in some instances increasing pressure even resulted in decreasing velocities. There are several possible explanations for this abnormal behavior, including the presence of gas, overconsolidation, or bimodal grain size distribution. The results indicate that an appropriate depth correction must be introduced into the published prediction equations in order to obtain reliable estimates of physical sediment properties for greater subsurface depths.     

Interannual Sea Level Variations and Annual Tides in the Northwestern Pacific

Specific properties of the interannual sea level variations and annual tides in the Northwestern Pacific were studied. Several tide stations were monitored. The monthly mean sea level for the year of 1995 was analyzed at each tide station. A seismic event in 1995, some tectonic activity around the subject area, and the Kuroshio (the oceanic western boundary current) may possibly contaminate results which would have occurred from the astronomical annual tide alone.     

Flow Cytometric Analysis of Coastal Lagoon Bacterioplankton and Picophytoplankton: Fixation and Storage Effects

The effect of different fixation and storage protocols on the flow cytometric (FCM) simultaneous analysis of bacterioplankton and phytoplankton in coastal seawater samples (Mediterranean coastal lagoons) was investigated. FCM measurements (cell number, fluorescence and scatter characteristics) were obtained through DAPI staining. Three fixatives [glutaraldehyde (GA), formaldehyde (FA) and paraformaldehyde (PFA)] and two storage (3 months duration) methods (5 °C and −196 °C) were tested. Two dominant populations were detected in studied samples: bacteria and eukaryotic picophytoplankton. Adding fixatives (2% final concentration) appears necessary to obtain FCM exhaustive counts of all the bacteria and phytoplanktonic cells. This was related to the permeation effect of fixatives which allowed a better DAPI staining of the cells. Maximum fluorescence, i.e. optimal staining of the cells was obtained with FA or PFA, and significant lower fluorescences with GA. Fixed samples stored at 5 °C induced rapid cell loss. Only storage in liquid nitrogen of samples fixed with FA or PFA, allows mid-term (≥4 months) preservation of bacteria or picophytoplankton cell numbers, and limited evolution of DAPI-induced fluorescence and scatter characteristics.     

INFORMATION FOR AUTHORS

<正>Acta Oceanologica Sinica(AOS)is a comprehensive academic journal edited by the Editorial Committee of Acta Oceanologica Sinica and is designed to provide a forum for important research papers of the marine scientific community which reflect the information on a worldwide basis.The journal publishes scholarly papers on marine science and technology,including physics,chemistry,biology,     

Net Sand Transport Direction in a Tidal Inlet, using Foraminiferal Tests as Natural Tracers

The relationship between the flux of exotic benthic foraminiferal tests (i.e. tests which are supplied from open-sea sources alone) in a tidal inlet and that of bulk sediment was analysed, which can be expressed as two first-order linear equations. According to this relationship, in order to determine net sediment transport directions in the entrance, the test concentration in surficial sediments of the tidal basin can be compared against a ‘ critical level ’. The critical level is determined for the conditions that no net transport of bulk sediment is present within the entrance. If the observed concentration (averaged over the tidal basin) is higher than the simulated critical level, then the net sediment transport is directed to landward. This method is applied to the analysis of net sand transport at Christchurch Harbour, a tidal inlet system located in southern England. In this investigation, concentrations of exotic foraminiferal tests in the surficial sediments of the tidal basin and ebb tidal delta area were obtained from the analysis of sea-bed sediment samples. A series of probable critical levels were calculated based upon the data sets with regard to: (1) sediment discharge from the rivers; (2) magnitude of sediment discharge within the entrance during the ebb; (3) the test concentration outside the harbour; (4) the thickness of the moving layer; and (5) two parameters associated with dispersive processes. The results show that the concentration in the tidal basin sediment is higher than a number of simulated critical concentrations for representative cases. Consequently, the high level of the concentration of exotic benthic foraminiferal tests within the harbour should be explained as a result of landward net transport of sands within the entrance.     

Dynamic behaviour of axially pre-loaded tubular steel members of offshore structures subjected to impact damage

The behaviour of an axially pre-loaded cylindrical member of an offshore structure, hit by a supply ship, has been investigated. The effects of axial pre-loading on the dynamic properties of members, the extent of damage and propagation of dynamic instability in the tubular members have also been investigated. Numerical models have been validated using available experimental data from the literature although these are mostly static with no pre-loading. Axial pre-loading was found to change the dynamic characteristics of some cylindrical members quite dramatically while it had no significant effect on others. The study examined whether there was any change in the behaviour between local and global modes when the loading was dynamic rather than static. The effect of damping on the dynamic instability of axially pre-loaded tubes under lateral dynamic loads was also studied. It was observed that for some geometries the quasi-static response can be used to define the boundary between bounded and unbounded dynamic responses. The main contribution of this study, compared with previous investigations reported in the literature, is that both pre-loading and dynamic effects have been included.     

Assessment of Impact on Seafloor Features in INDEX Area

Observations on seafloor features from subbottom profiling and seabed photography data show that the undisturbed and natural conditions before the benthic disturbance undergo a substantial change after operation of the disturber. The effects can be seen in the form of deep trenches and grooves, formed by the action of the sleds and the pumping of the sediment along its path, as well as sediment piles on either side of the track. Biological traces such as fecal coils, casts, tubes, burrows, and trails get obliterated in the areas of disturbance and resedimentation. The smooth, uniform nature of the seafloor observed in predisturbance phase shows microtopographic changes in and around the disturbed area as a result of sediment excavation and resettlement. Vertical mixing as well as lateral transport of sediment alter the geological, biological, physical, and chemical conditions on the seafloor, which need to be monitored over time to assess the process and the time taken for restoration of environmental conditions.     

Regional Commercial Sponge Extinctions in the West Indies: Are Recent Climatic Changes Responsible?

Abstract. Long-term changes in the distributional patterns of commercial sponges ( Spongia spp. and Hippospongia spp.) within the West Indian Region indicates that: 1) commercial sponges had a widespread distribution throughout the whole West Indian Region and were ubiquitous in very shallow water until about the first half of the present century; 2) they were fished commercially not only in the traditional northern Caribbean sites (Florida, Gulf of Mexico, Bahamas) but also in the Greater ( e. g. , Hispaniola, Jamaica) and Lesser Antilles; and 3) they became extinct throughout most of the Lesser Antilles ( e. g. , Puerto Rico, Vieques, St. Thomas) sometime during the first half of this century. Mortalities of spongiids within the Antilles were found to differ from other marine mortalities in that: 1) species disappeared from a large region; 2) species vanished from different habitats and depths; and 3) natural populations never recovered. Species richness patterns suggest that commercial sponge genera ( Spongia and Hippospongia ) evolved under slightly cooler elimatic conditions than those found at present, and that these extinctions occurred as a direct or indirect effect of positive thermal anomalies in sea surface and atmospheric temperatures between 1900–1950. The concept that species diversity is stable on a regional scale is questioned.