基于影像纹理特征和外部风向的星载 SAR 海面风场反演研究

在合成孔径雷达(Synthetic Aperture Radar,SAR)海面风场反演中,基于风条纹影像纹理特征的海面风向反演方法精度高,但是依赖于图像风条纹的存在,而外部风向信息与SAR资料时空分辨率不易匹配、精度较低,从而影响大面积、高分辨率海面风场反演的精度。针对此问题,提出一种将SAR图像风条纹线性纹理特征与外部风向信息相结合的星载SAR海面风向获取方法,在SAR影像线性纹理特征明显的区域采用二维连续小波变换得到高精度的海面风向,其余区域采用与之时空相匹配的数值预报模式风向填充;并利用地球物理模型函数进一步得到海面风速,进而实现高精度、大范围海面风场的反演。为验证本文方法的有效性,利用ENVISAT/ASAR数据进行风场反演试验,并将反演结果与浮标实测数据进行比对。结果表明:在线性纹理特征明显的区域,小波方法的反演精度优于快速傅里叶变换(FFT)法和数值预报模式风向;外部风向精度略低,但与SAR观测资料时空匹配性较好,弥补了风条纹风向的不足。二者的结合为星载SAR海面风场反演的业务化应用提供了支持。     

The interplay of sediment characteristics,depth, water temperature,and ocean currents shaping the biogeography of lancelets (Subphylum Cephalochordata) in the NW Pacific waters

Lancelets (or amphioxus) are often found within the soft bottom of shallow tropical and temperate seas. The present study is the first to provide a fine‐scale biogeography of five species of lancelets (Asymmetron lucayanum, Branchiostoma belcheri, Branchiostoma japonicum, Epigonichthys cultellus, and Epigonichthys maldivensis) in the NW Pacific and examine the effects of multiple environmental parameters. From multivariate analyses, the distribution and abundance patterns of lancelets were explained by a combination of factors comprising depth, temperature of the collecting month, mean temperature of the coldest month in the year, medium particle size and silt/clay ratio of the sediments. In addition, ocean currents also affect their distribution range. The major occurrence of A. lucayanum and E. maldivensis was associated with the warm Kuroshio current, but E. maldivensis exhibited higher tolerance to low salinity and low temperature, and preferred substrata of slightly larger grain size, a lower ratio of suspended sediments, and deeper water. The closely related B. belcheri and B. japonicum exhibited fine‐scale habitat differentiation, and B. japonicum was abundant along the southern coast of China, where the salinity is lower in winter because of the China Coastal Current and the substratum is composed of very coarse sand with suspended sediments. Branchiostoma belcheri occurred in low abundance and was only recorded in Northern Taiwan and the Taiwan Banks. Epigonichthys cultellus was found only at the Taiwan Banks, which had deep water, coarse sand, and a negligible amount of suspended sediments.     

面向海洋监测的传感数据可用性评价技术

无线传感器网络已成为监测海洋环境信息的一种重要手段,然而由于传感设备部署的范围和密度不同,造成不同位置的感知数据的可用性差异很大,针对此建立模型并进行评价对于高质量的数据获取和清洗具有重要的意义。基于传感器节点的感知模型、能耗模型和改进的Leeway漂流模型,面向感知数据的可靠性和时效性两个方面,建立了围绕海洋监测应用的综合评判指标,进一步提出数据采集船航行路线的评价方法和数据源的选择方法,最后通过实验验证了提出模型和方法的有效性。     

基于实密度的卧式浪流轮机水槽实验研究分析

实密度是影响轮机获能特性的关键因素之一。文中以卧式轮机实密度为基变量,以其获能系数为主要考察点,对3种实密度卧式轮机进行水槽实验方案设计和水动力性能研究。实验分别对水流流速、轮机旋转角速度、主轴转矩以及功率进行测量,并对其对主轴的扭矩、轮机的获能系数以及叶片的旋转特性进行定量分析,最终证实了该卧式轮机的单一运行特性。通过绘制基于实密度的轮机转矩—转角曲线、获能系数—尖速比曲线和轮机功率—尖速比曲线,阐明了实密度影响卧式轮机获能水动力性能的规律,即其获能系数和发电功率都随着工况速比呈先增后降趋势。实密度较低轮机因浪流流失而获得能量小,但实密度过高轮机会导致叶片间湍流涌动,加速叶片失速特性而影响轮机获能。这为卧式浪流轮机结构优化提供了可靠依据和借鉴。     

海洋数据同化与数据融合技术应用综述

简述了不同数据同化和数据融合方法在海洋环境监测与预测方面的应用、国内外相关业务单位的海洋分析和预报系统的现状,以及海洋数据同化将来的业务化应用的发展趋势。四维变分和集合卡尔曼滤波正在成为国际上海洋环境分析与预报的主要应用方向,海-气耦合数据同化以及海冰数据同化是目前数据同化方法研究的热点。     

IMPROVEMENT OF OCEAN DATA ASSIMILATION SYSTEM AND CLIMATE PREDICTION BY ASSIMILATING ARGO DATA

The Argo(Array for Real-time Geostrophic Oceanography) data from 1998 to 2003 were used in the Beijing Climate Center-Global Ocean Data Assimilation System(BCC-GODAS). The results show that the utilization of Argo global ocean data in BCC-GODAS brings about remarkable improvements in assimilation effects. The assimilated sea surface temperature(SST) of BCC-GODAS can well represent the climatological states of observational data. Comparison experiments based on a global coupled atmosphere-ocean general circulation model(AOCGM) were conducted for exploring the roles of ocean data assimilation system with or without Argo data in improving the climate predictability of rainfall in boreal summer. Firstly, the global ocean data assimilation system BCC-GODAS was used to obtain ocean assimilation data under the conditions with or without Argo data. Then, the global coupled atmosphere-ocean general circulation model(AOCGM) was utilized to do hindcast experiments with the two sets of the assimilation data as initial oceanic fields. The simulated results demonstrate that the seasonal predictability of rainfall in boreal summer, particularly in China, increases greatly when initial oceanic conditions with Argo data are utilized. The distribution of summer rainfall in China hindcast by the AOGCM under the condition when Argo data are used is more in accordance with observation than that when no Agro data are used. The area of positive correlation between hindcast and observation enlarges and the hindcast skill of rainfall over China in summer improves significantly when Argo data are used.     

海洋声学层析研究现状与展望

海洋声层析是1979年美国科学家W.Munk等人提出的,通过测量传播时间等声传播信号有关参量反演声波所穿越的海洋特征,得到大面积海域中的海洋动力学状态及其变化的估计。声层析方法自提出以来受到各国的重视。在最初的20 a间,以全球测温计划(ATOC)为代表的一系列验证实验推动了声层析的理论研究、设备研制和应用。步入21世纪后,声层析与海洋动力学的数据同化、利用滑翔机等设备的移动声层析以及沿海声层析得到重视,并进行了相关的理论与实验研究。纳入成像旗下的声层析希尔伯特方法、有效低功耗的分布式传感网络声层析,以及被动声层析,或将成为声层析未来研究的重要方向。     

PCBs and its coupling with eco-environments in Southern Yellow Sea surface sediments

In this paper, the spatial distribution and source of the PCBs in surface sediments of the Southern Yellow Sea (SYS) and influencing factors, such as the sediment characteristics (components, relative proportions and total organic carbon contents), and hydrodynamic conditions were analyzed. PCB concentrations in the surface sediments ranged from 518-5848 pg/g, with average values of 1715 pg/g decreasing sharply compared to last year. In the study area, the PCB pollution level in the middle area was the highest, followed by that of the east coast and the west coast, respectively. Although the PCB level in the coastal areas was lower than that in the middle areas, it was proven in our study that the Yellow Sea obtained PCBs by virtue of river inputs. There was a positive and pertinent correlation between the clay proportion and PCB concentrations, and the increase of the PCB concentrations was directly proportional to the increase of TOC contents, with r=0.61, but it was contrary to the sediment grain size. Consequently, the factors controlling PCB distribution had direct or indirect relationships with sediment grain size; moreover, the hydrodynamic conditions determined the sediment components and grain size. In conclusion, hydrodynamic conditions of the Yellow Sea were the most important influencing factors effecting the distribution of PCBs in the surface sediments of the SYS.     

Performance comparison of two biotic indices measuring the ecological status of water bodies in the Southern Baltic and Gulf of Lions

Two biotic indices, ATZI Marine Biotic Index (AMBI) and Benthic Quality Index (BQI) have been recently introduced within the EC Water Framework Directive to assess the quality of marine habitats: both are based on sensitivity/tolerance classification and quantitative information on the composition of soft-bottom macrofauna. Their performance, especially with regard to sampling effort was assessed based on two data sets collected in Southern Baltic and one from the Gulf of Lions Mediterranean. AMBI was not affected by sampling effort but BQI was. Two modifications were proposed for BQI (i.e., BQI) (1) the removal of the scaling term (i.e., BQI(W)), and (2) the replacement of the scaling term by different scaling term (i.e., BQI(ES)). Both modified BQIs were largely independent of sampling effort. Variability was slightly lower for BQI(W) than for BQI(ES). BQI was highly correlated with BQI(W) and with BQI(ES) both in the Southern Baltic and in the Gulf of Lions. However, the proportions of stations, which were not attributed the same ecological quality status (EcoQ) when using BQI and its two modified forms were always high. Differences in ecological classification were mostly due to the scales used to infer EcoQ. Based on this study we recommend to use BQI(ES) in future studies because it apparently constitutes the best compromise in (1) being independent of sampling effort, (2) limiting the variability in computation in relation with sampling effort, (3) being correlated with BQI and corresponding EcoQ.     

Palaeomagnetic results from the Early Permian Copacabana Group, southern Peru: Implication for Pangaea palaeogeography

Samples collected from folded carbonate rocks of the Early Permian Copacabana Group exposed in the Peruvian Subandean Zone have been subjected to detailed palaeomagnetic analysis. Thermal demagnetisation of most samples yield stable high unblocking temperature directions dominantly carried by titanomagnetite minerals. This remanence, identified in 32 samples (43 specimens), is exclusively of reverse polarity consistent with the Permian–Carboniferous Reversal Superchron (PCRS). The overall directions pass the fold test at the 99% confidence level and are considered as being a pre-folding remanence acquired in Early Permian times. The Copacabana Group yields an overall mean direction of D = 166°, I = +49° (α₉₅ = 4.5°, k = 131.5, N = 9 sites) in stratigraphic coordinates and a corresponding palaeosouth pole position situated at λ = 68°S,  = 321°E (A₉₅ = 5.2°, K = 100). Combining this pole with the coeval high quality data from South America, Africa and Australia results in a mean pole for Gondwana situated at λ = 34.4°S,  = 065.6°E (A₉₅ = 4.9°, K = 73.6, N = 13 studies) in African coordinates. This pole position supports a Pangaea B palaeogeography in Early Permian times. In contrast, the combined pole for Gondwana diverges from the coeval Laurasian mean pole when assuming the Pangaea A-type configuration. Poor quality of the Gondwana dataset and inclination shallowing in sediments seem to play no role in the misfit between the Permian–Triassic poles from Gondwana and Laurasia in Pangaea A reconstruction.