A dynamically consistent analysis of circulation and transports in the southwestern Weddell Sea     

M. Yaremchuk  D. Nechaev  J. Schroter  E. Fahrbach 《Annales Geophysicae》1998,16(8):1024-1038

An inverse model is applied for the analysis of hydrographic and current meter data collected on the repeat WOCE section SR4 in the Weddell Sea in 1989–1992. The section crosses the Weddell Sea cyclonic gyre from Kapp Norvegia to the northern end of the Antarctic Peninsula. The concepts of geostrophy, conservation of planetary vorticity and hydrostatics are combined with advective balances of active and passive properties to provide a dynamically consistent circulation pattern. Our variational assimilation scheme allows the calculation of three-dimensional velocities in the section plane. Current speeds are small except along the coasts where they reach up to 12 cm/s. We diagnose a gyre transport of 34 Sverdrup which is associated with a poleward heat transport of 28 × 10¹² W corresponding to an average heat flux of 15 Wm^–2 in the Weddell Sea south of the transect. This exceeds the estimated local flux on the transect of 2 Wm^–2. As the transect is located mostly in the open ocean, we conclude that the shelf areas contribute significantly to the ocean-atmosphere exchange and are consequently key areas for the contribution of the Weddell Sea to global ocean ventilation. Conversion of water masses occuring south of the section transform 6.6 ± 1.1 Sv of the inflowing warm deep water into approximately equal amounts of Weddell Sea deep water and Weddell Sea bottom water. The volume transport of surface water equals in the in-and outflow. This means that almost all newly formed surface water is involved in the deep and bottom water formation. Comparison with the results obtained by pure velocity interpolation combined with a hydrographic data subset indicates major differences in the derived salt transports and the water mass conversion of the surface water. The differences can be explained by deviations in the structure of the upper ocean currents to which shelf areas contribute significantly. Additionally a rigorous variance analysis is performed. When only hydrographic data are used for the inversion both the gyre transport and the poleward heat transport are substantially lower. They amount to less than 40% of our best estimate while the standard deviations of both quantities are 6.5 Sv and 37 × 10¹² W, respectively. With the help of long-term current meter measurements these errors can be reduced to 2 Sv and 8 × 10¹² W. Our result underlines the importance of velocity data or equivalent information that helps to estimate the absolute velocities.  相似文献   

云南民族语地名探析   总被引：1，自引：0，他引：1  

朱惠荣 《云南地理环境研究》1994,6(1):11-22

云南有２５种世居的少数民族，是全国少数民族最多的省，也是民族语地名语种最多的省。云南被称为“地名博物馆，，民族语地名有其典型性。云南的民族语地名有很多特点，但并不特殊，在其他地方也似曾相识。本文以一个省为单元，对少数民族语地名进行全面综合研究，探讨民族语地名与地理环境、历史发展的关系及各种民族语地名之间的关系。  相似文献   

ISA accelerometer onboard the Mercury Planetary Orbiter: error budget     

Valerio Iafolla  David M. Lucchesi  Sergio Nozzoli  Francesco Santoli 《Celestial Mechanics and Dynamical Astronomy》2007,97(3):165-187

We have estimated a preliminary error budget for the Italian Spring Accelerometer (ISA) that will be allocated onboard the Mercury Planetary Orbiter (MPO) of the European Space Agency (ESA) space mission to Mercury named BepiColombo. The role of the accelerometer is to remove from the list of unknowns the non-gravitational accelerations that perturb the gravitational trajectory followed by the MPO in the strong radiation environment that characterises the orbit of Mercury around the Sun. Such a role is of fundamental importance in the context of the very ambitious goals of the Radio Science Experiments (RSE) of the BepiColombo mission. We have subdivided the errors on the accelerometer measurements into two main families: (i) the pseudo-sinusoidal errors and (ii) the random errors. The former are characterised by a periodic behaviour with the frequency of the satellite mean anomaly and its higher order harmonic components, i.e., they are deterministic errors. The latter are characterised by an unknown frequency distribution and we assumed for them a noise-like spectrum, i.e., they are stochastic errors. Among the pseudo-sinusoidal errors, the main contribution is due to the effects of the gravity gradients and the inertial forces, while among the random-like errors the main disturbing effect is due to the MPO centre-of-mass displacements produced by the onboard High Gain Antenna (HGA) movements and by the fuel consumption and sloshing. Very subtle to be considered are also the random errors produced by the MPO attitude corrections necessary to guarantee the nadir pointing of the spacecraft. We have therefore formulated the ISA error budget and the requirements for the satellite in order to guarantee an orbit reconstruction for the MPO spacecraft with an along-track accuracy of about 1 m over the orbital period of the satellite around Mercury in such a way to satisfy the RSE requirements.  相似文献   

A global map to aid the identification and screening of critical habitat for marine industries     

《Marine Policy》2015

Marine industries face a number of risks that necessitate careful analysis prior to making decisions on the siting of operations and facilities. An important emerging regulatory framework on environmental sustainability for business operations is the International Finance Corporation’s Performance Standard 6 (IFC PS6). Within PS6, identification of biodiversity significance is articulated through the concept of “Critical Habitat”, a definition developed by the IFC and detailed through criteria aligned with those that support internationally accepted biodiversity designations. No publicly available tools have been developed in either the marine or terrestrial realm to assess the likelihood of sites or operations being located within PS6-defined Critical Habitat. This paper presents a starting point towards filling this gap in the form of a preliminary global map that classifies more than 13 million km² of marine and coastal areas of importance for biodiversity (protected areas, Key Biodiversity Areas [KBA], sea turtle nesting sites, cold- and warm-water corals, seamounts, seagrass beds, mangroves, saltmarshes, hydrothermal vents and cold seeps) based on their overlap with Critical Habitat criteria, as defined by IFC. In total, 5798×10³ km² (1.6%) of the analysis area (global ocean plus coastal land strip) were classed as Likely Critical Habitat, and 7526×10³ km² (2.1%) as Potential Critical Habitat; the remainder (96.3%) were Unclassified. The latter was primarily due to the paucity of biodiversity data in marine areas beyond national jurisdiction and/or in deep waters, and the comparatively fewer protected areas and KBAs in these regions. Globally, protected areas constituted 65.9% of the combined Likely and Potential Critical Habitat extent, and KBAs 29.3%, not accounting for the overlap between these two features. Relative Critical Habitat extent in Exclusive Economic Zones varied dramatically between countries. This work is likely to be of particular use for industries operating in the marine and coastal realms as an early screening aid prior to in situ Critical Habitat assessment; to financial institutions making investment decisions; and to those wishing to implement good practice policies relevant to biodiversity management. Supplementary material (available online) includes other global datasets considered, documentation and justification of biodiversity feature classification, detail of IFC PS6 criteria/scenarios, and coverage calculations.  相似文献   

The roughness of the dark side of Iapetus from the 2004 to 2005 flyby     

Janice S. Lee  Bonnie J. Buratti  Joel Mosher 《Icarus》2010,206(2):623-630

The roughness of a planetary surface offers clues to its past geologic history. We apply a surface roughness model developed by Buratti and Veverka (Buratti, B.J., Veverka, J. [1985]. Icarus 64, 320-328) to Cassini ISS data from the January 1st, 2005 flyby of Iapetus. This model uses the observed scattering behavior to provide a depth to radius factor q quantifying the size of idealized craters on the surface. Our findings indicate that the surface on the dark side is significantly smoother than the surfaces of other icy low-albedo saturnian satellites. We have found that the average depth to radius on the leading (dark) side is 0.084, corresponding to a Hapke mean slope angle of 6°. As compared to the 13-33° Hapke mean slope angle of other icy satellites (Buratti, B.J., and 10 colleagues [2008]. Icarus 193, 309-322), our results present a clearly different picture for the leading surface of Iapetus, suggesting that the dark deposit contributes to the decrease in macroscopic surface roughness of the leading side. Attempts were made to obtain an average depth to radius value for the trailing (bright) side; however the scans of the bright side from this flyby exhibited large variations in albedo, resulting in results that were physically unrealistic.  相似文献   

半封闭海域生态修复策略研究——以渤海为例          下载免费PDF全文

张少春  宋静静  刘凯凯  于道德  李友训  马健  李彬  王先磊 《海洋开发与管理》2022,39(9):3-10

渤海作为我国唯一的半封闭型海域,是京津冀城市群蓬勃发展的战略支撑和关键依托,其生态环境的稳定与沿岸人类福祉息息相关,其生态环境修复是近年来该领域的研究热点。文章重点围绕全球气候变化和人类活动对渤海生态环境的影响进行了剖析,通过综合对比分析国内外其他类似水域或地区的生态修复既有成果,立足渤海水域特点和现状,提出动态思维与整体保护原则、生境连通性修复原则、不同时空尺度修复原则等生态修复原则,并指出渤海生态修复需理性规划渔业经济活动,统筹考虑渤海生态与冲淡水之间的关系,建议运用前瞻性的思维模式和理念,合理预测、规划、定位、配置、实施和维护渤海生态系统的稳定,重点探索应对全球气候变化的最佳适应性管理策略。  相似文献   

Sustaining marine life beyond boundaries: Options for an implementing agreement for marine biodiversity beyond national jurisdiction under the United Nations Convention on the Law of the Sea     

《Marine Policy》2014

For nearly a decade, governments have been discussing the need to improve efforts to conserve and sustainably use marine biodiversity in areas beyond national jurisdiction (ABNJ). Support for a new international agreement under the United Nations Convention on the Law of the Sea (UNCLOS) – an Implementing Agreement – on the conservation and sustainable use of marine biodiversity in ABNJ has been growing. In June 2012, at the United Nations Conference on Sustainable Development held in Rio de Janeiro, Brazil, States agreed to take a decision on the development of an international instrument under UNCLOS before the end of the 69th session of the United Nations General Assembly (UNGA), which runs from September 2014 to August 2015. In follow-up to this commitment, it was agreed to consider the “scope, parameters and feasibility” of this instrument. To inform these international discussions, this article highlights some potential options for the content of a new UNCLOS Implementing Agreement. It first reviews the history of UN discussions, and then elaborates on options to address key elements identified as priorities for States in 2011: marine genetic resources, including the sharing of benefits, area-based management tools, including marine protected areas, environmental impact assessments, capacity-building and the transfer of marine technology. It addresses cross-cutting issues such as the governing principles, institutional structure as well as on other critical points such as High Seas fishing and flag State responsibilities. The article concludes with suggestions on possible next steps in order to succeed in the negotiations for an agreement.  相似文献   

Remote sensing of scattered Natura 2000 habitats using a one-class classifier     

《International Journal of Applied Earth Observation and Geoinformation》2014

Mapping of habitats with relevance for nature conservation involves the identification of patches of target habitats in a complex mosaic of vegetation types not relevant for conservation planning. Limiting the necessary ground reference to a small sample of target habitats would greatly reduce and therefore support the field mapping effort. We thus aim to answer in this study the question: can semi-automated remote sensing methods help to map such patches without the need of ground references from sites not relevant for nature conservation? Approaches able to fulfill this task may help to improve the efficiency of large scale mapping and monitoring programs such as requested for the European Habitat Directive.In the present study, we used the maximum-entropy based classification approach Maxent to map four habitat types across a patchy landscape of 1000 km² near Munich, Germany. This task was conducted using the low number of 125 ground reference points only along with easily available multi-seasonal RapidEye satellite imagery. Encountered problems include the non-stationarity of habitat reflectance due to different phenological development across space, continuous transitions between the habitats and the need for improved methods for detailed validation.The result of the tested approach is a habitat map with an overall accuracy of 70%. The rather simple and affordable approach can thus be recommended for a first survey of previously unmapped areas, as a tool for identifying potential gaps in existing habitat inventories and as a first check for changes in the distribution of habitats.  相似文献   

地质工程专业普通地质认识实习教学的思考     

许宝田  张勇  王博  杨爱华  解国爱 《高校地质学报》2022,28(3):382-386

文章针对地质工程专业中基础地质学的重要性和普地实习野外教学实际,提出在普地实习中融入地质工程专业知识教学内容。从岩石基本地质特征、力学问题和具体工程地质问题3个方面将基础地质学与地质工程专业知识进行融合、交叉。从而拓展学生视野,实现实习模式创新、内容改革,促进学生学习意识和自主学习的发展,提升专业思维。岩石成分与岩石力学性质、风化特征和水软化性关系密切,节理面的粗糙、起伏和充填物成分影响节理面抗剪、透水等特性,具体工程中的“滑坡”问题是典型的岩体剪切破坏问题,其形成的力学机制与剪节理相同。将上述问题两者联系起来的讲解丰富了普地实习的内容。文章认为普地实习中观察到的现象与地质工程专业课程中很多知识点紧密联系,在基础地质实习教学中融入上述地质工程的专业知识是完全可行性的,采取增加与地质工程专业结合的实践教学环节的办法,既扩大了学生知识面,初步提高学生专业素养,也为实现毕业后成为专业领域合格工程师和科研人员的培养目标迈出重要的第一步。  相似文献   

Habitat modeling for health sovereignty: Increasing indigenous access to medicinal plants in northern Maine,USA     

《Applied geography (Sevenoaks, England)》2015

Medicinal plants and fungi play important roles in the health of Maliseet people of northern Maine, USA. A critical aspect of exercising choice in health care for this community is the ability to locate and have access to these plants. Habitat suitability modeling is a form of geospatial technology that can enhance health sovereignty by identifying locations in which populations of medicinal plants can be conserved or established. However, use of this technology within indigenous communities has been limited. Focusing on the medicinal plant muskrat root, Acorus americanus (Raf.) Raf., we generate a habitat suitability model for eastern Aroostook County, Maine (1,055,653.659 ha) that also takes community needs into consideration. Drawing on participatory ethnographic data as well as environmental characteristics, our model combines ecological and sociocultural parameters to identify previously unknown populations of A. americanus that are accessible to tribal elders. Our model successfully predicted 95% of A. americanus locations in our field validation data set of ∼71,000 ha. Results suggest that approximately 0.6% of our study area contains suitable habitat to plant muskrat root that could also meet tribal members' gathering needs for the future. Increasing the number of potential collection sites gives communities options for gathering, thereby enhancing health sovereignty. Broadly, our work suggests that, when done in partnership with communities, different forms of geospatial technology can be beneficial tools for efforts to promote health sovereignty.  相似文献