Namibia's orange river boundary — origin and reemerged effects of an inattentive colonial boundary delimination     

Imre Josef Demhardt 《GeoJournal》1990,22(3):355-362

Conclusion From the above and beside the securing of water rights for the national mining industry, the irrigation clusters scattered as if pearls along the Orange River's N bank are of an obviously unrenouncable significance for the Namibian agricultural production. In any case, it is clearly of utmost importance for Windhoek to secure the possession of the N flood plain by a boundary accord to be reached as soon as possible. This should determine as a minimal solution the border line finally along the low water mark, or, certainly more advantageous for the country, following the rivers median line. Even more so because, in spite of the high costs this would entail due to the lack of infrastructure in the inaccessible Orange gorge, the future extending potential of the irrigation schemes on the N bank are be estimated at least on 7800 ha (Otzen 1989) which is six times the developed irrigation area at the present stage and more than the actual overall Namibian irrigated cultivation area.In order to strengthen the claim to all areas presently disputed between the Republics of Namibia and South Africa and backed by several in international law not binding UN General Assembly resolutions, the Windhoek Constitutional Assembly resolved Article 1 (4) of the new Namibian constitution: The national of Namibia shall consist of the whole of territory recognised by the international community through the organs of the United Nations as Namibia, including the enclave, harbour and port of Walvis Bay, as well as the off-shore islands of Namibia, and its southern boundary shall extend to the middle of the Orange River. Secret negotiations have been taking place since 21st March 1990 but as in the case of the much disputed possession of Walvis Bay, the Republic of South Africa cannot be forced to accept the low water line or the now constitutionally claimed median line as the revised Orange River boundary. South Africa remains internationally unsuable and the small Namibia is presently unable to put pressure on the leading regional power. On the contrary, such a substantial revision of the failures of the late German colonial administration seems only be attainable, if it all, after a phase of positive development in Windhoek, so to be recognised by Pretoria, which then could be result in a voluntary surrender of the South African claim to the N bank to seal then hopefully reached good neighbourly relations between the Republic of South Africa and the recently emerged Republic of Namibia.  相似文献   

An upper‐ocean general circulation model for the north pacific: Preliminary experiments     

Josef Cherniawsky  Greg Holloway 《大气与海洋》2013,51(4):737-784

Abstract

A model with two active layers, a mixed layer and a pycnocline layer, over a semipassive deep ocean is described. The model is used to simulate a climatological seasonal cycle in the upper North Pacific. The formulation is similar to that in Cherniawsky et al. (1990). The model resolution is 1° latitude by 1.5° longitude, extending from 62°N to the equator. It is driven with monthly wind stress (Hellerman and Rosenstein, 1983) and with Newtonian heat and freshwater fluxes, which were inferred from climatological (Levitus, 1982) sea‐surface monthly temperatures and annual mean salinities. The monthly temperature anomalies (without the annual mean) are multiplied by a prescribed gain factor and advanced in time, compensating for time delay in the response of the mixed layer. No‐slip and no‐flux constraints are applied on north, east, west and land boundaries, while the following open boundary conditions are used at the equator: (a) free‐slip on zonal velocities in the two layers; (b) a prescribed meridional transport, due to local curl of the wind stress, in the mixed layer; (c) an antisymmetric meridional velocity plus a small flux‐balancing term in the second layer; and (d) across‐equator symmetry for layer depths, temperatures and salinities. Sensitivity to two aspects of parametrization is investigated: (1) the change to horizontal diffusion/viscosity coefficients that depend on the velocity deformation field (as in Smagorinsky, 1963), and (2) the use of idealized piecewise‐linear profiles for second‐layer temperatures and salinities for calculating mixed layer entrainment fluxes.  相似文献   

Effects of water temperature on summer periphyton biomass in shallow lakes: a pan-European mesocosm experiment     

Aldoushy Mahdy  Sabine Hilt  Nur Filiz  Meryem Beklioğlu  Josef Hejzlar  Deniz Özkundakci  Eva Papastergiadou  Ulrike Scharfenberger  Michal Šorf  Kostas Stefanidis  Lea Tuvikene  Priit Zingel  Martin Søndergaard  Erik Jeppesen  Rita Adrian 《Aquatic Sciences - Research Across Boundaries》2015,77(3):499-510

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Seasonal variation of the <Emphasis Type="Italic">M</Emphasis><Subscript>2</Subscript> tide     

Malte?MüllerEmail author  Josef?Y.?Cherniawsky  Michael?G.?G.?Foreman  Jin-Song?von?Storch 《Ocean Dynamics》2014,64(2):159-177

The seasonal cycle of the main lunar tidal constituent M ₂ is studied globally by an analysis of a high-resolution ocean circulation and tide model (STORMTIDE) simulation, of 19 years of satellite altimeter data, and of multiyear tide-gauge records. The barotropic seasonal tidal variability is dominant in coastal and polar regions with relative changes of the tidal amplitude of 5–10 %. A comparison with the observations shows that the ocean circulation and tide model captures the seasonal pattern of the M ₂ tide reasonably well. There are two main processes leading to the seasonal variability in the barotropic tide: First, seasonal changes in stratification on the continental shelf affect the vertical profile of eddy viscosity and, in turn, the vertical current profile. Second, the frictional effect between sea-ice and the surface ocean layer leads to seasonally varying tidal transport. We estimate from the model simulation that the M ₂ tidal energy dissipation at the sea surface varies seasonally in the Arctic (ocean regions north of 60°N) between 2 and 34 GW, whereas in the Southern Ocean, it varies between 0.5 and 2 GW. The M ₂ internal tide is mainly affected by stratification, and the induced modified phase speed of the internal waves leads to amplitude differences in the surface tide signal of 0.005–0.0150 m. The seasonal signals of the M ₂ surface tide are large compared to the accuracy demands of satellite altimetry and gravity observations and emphasize the importance to consider seasonal tidal variability in the correction processes of satellite data.  相似文献   

Iterative Spherical Downward Continuation Applied to Magnetic and Gravitational Data from Satellite   总被引：1，自引：0，他引：1  

Josef Sebera  Michal Šprlák  Pavel Novák  Aleš Bezděk  Miloš Vaľko 《Surveys in Geophysics》2014,35(4):941-958

In the last few decades, satellites have acquired various potential data sets hundreds of kilometers above the Earth’s surface. Conventionally, these global magnetic and gravitational data sets are approximated by using spherical harmonics that allow straightforward work with both fields outside the Earth’s mass. In this article, we present an alternative approach for working with potential data in mass-free space given over a regular coordinate grid on a spherical surface. The algorithm is based on an iterative scheme and the Poisson integral equation for the sphere. With help from the Fourier transform, global potential (magnetic or gravitational) data can efficiently be continued from a mean orbital sphere down to a reference surface without using the spherical harmonics. This is illustrated both with simulated magnetic field data and with real data from the satellite gradiometry mission GOCE. In the case of simulated magnetic data and the downward continuation for 450 km, we have achieved a root mean square at the level of 0.05 nT, while it was <1 E (eotvos) for real GOCE data continued for 250 km. The crucial point is to apply the algorithm twice as a large part of noise can be removed from the input data.  相似文献   

Paleotopographic controls on loess deposition in the Loess Plateau of China   总被引：3，自引：0，他引：3       下载免费PDF全文

Li‐Yang Xiong  Guo‐An Tang  Josef Strobl  A‐Xing Zhu 《地球表面变化过程与地形》2016,41(9):1155-1168

The underlying pre‐existing paleotopography directly influences the loess deposition process and shapes the morphology of current loess landforms. An understanding of the controlling effects of the underlying paleotopography on loess deposition is critical to revealing the mechanism of loess‐landform formation. However, these controlling effects exhibit spatial variation as well as uncertainty, depending on a study's data sources, methodologies and particular research scope. In this study, the geological history of a study area in the Loess Plateau of China that is subject to severe soil erosion is investigated using detailed geological information and digital elevation models (DEMs), and an underlying paleotopographic model of the area is constructed. Based on the models of modern terrain and paleotopography, we introduce a watershed hierarchy method to investigate the spatial variation of the loess‐landform inheritance relationship and reveal the loess deposition process over different scales of drainage. The landform inheritance relationships were characterized using a terrain‐relief change index (TRCI) and a bedrock terrain controllability index (BTCI). The results show that the TRCI appears to have an inverse relationship with increasing research scope, indicating that, compared with the paleotopography of the region, modern terrain has lower topographic relief over the entire area, while it has higher topographic relief in the smaller, local areas. The BTCI strengthens with increasing drainage area, which demonstrates a strong controlling effect over the entire study area, but a weak effect in the smaller, local areas because of the effect of paleotopography on modern terrain. The results provide for an understanding of the spatial variation of loess deposition in relation to paleotopography and contribute to the development of a process‐based loess‐landform evolution model. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Depth limit of littoral vegetation in a storage reservoir: A case study of Lipno Reservoir (Czech Republic)     

Monika Krolová  Hana ?í?kováJosef Hejzlar 《Limnologica》2012,42(2):165-174

Controlling factors for the occurrence of littoral macrophyte species were investigated in Lipno Reservoir (area: 46.5 km²; z_mean: 6.6 m; z_max: 22 m; water residence time: 0.6 yr), a dam impoundment with moderately fluctuating water level (amplitude up to 4 m) which is used for hydropower and downstream flow augmentation. The options of supporting littoral macrophyte growth for improving the reservoir's ecological potential were evaluated according to the European Water Framework Directive's definitions. Macrophytes were examined at 115 sites, each 50 m long, along the whole reservoir perimeter at regular 1 km intervals. Sites were surveyed for their phytocoenology, shore morphometry, pedological characteristics of substrate, transparency of water, and anthropogenic impacts. Most of the sites were characterised by a wide eulittoral zone with a tenuous cover of terrestrial hydrophilic, amphibious, and/or emergent macrophytes and a low proportion of silt, clay, and organic fractions in the substrate. Infralittoral submerged and floating-leaved macrophytes were restricted to a few sites within the mouths of the main and side tributaries where transparency was maintained by clear inflow water independent of reservoir pool fluctuations. Water transparency was low (1-2 m) compared to annual changes of water level (2 to >3 m). Multivariate statistical analysis (DCA, CCA) confirmed relationships between the occurrence of macrophyte species and morphological and substrate characteristics of the shore. Improvement of macrophyte cover and establishment of vital infralittoral zones requires improvements in water transparency and changes in reservoir operation, i.e., limiting the range of water level fluctuation to less than ca. 1 m.  相似文献   

Biological and ecological mechanisms for overcoming sperm limitation in invasive dreissenid mussels     

Noel P. Quinn  Josef D. Ackerman 《Aquatic Sciences - Research Across Boundaries》2012,74(3):415-425

Many broadcast-spawning benthic invertebrates are subject to sperm limitation yet achieve high population densities, as for example dreissenid mussels (Dreissena polymorpha and Dreisssena bugensis) that were introduced into the Laurentian Great Lakes. The question remains whether biological or ecological/physical mechanisms reduce sperm limitation. Gamete dilution/longevity experiments were undertaken to determine whether dreissenid mussels are subject to sperm limitation, and computational fluid dynamic modeling was used to determine the potential influence of bottom roughness on sperm dilution in nature. Results indicated that dreissenid mussels may be sperm limited, but the extent to which sperm dilution affects them is lower than what was reported for other broadcast spawning invertebrates. Importantly, model mussel clusters influenced external fertilization by retaining sperm in downstream eddies but allowing downstream transport from one cluster to another. This, in addition to high sperm potency at low sperm concentrations, may help to explain the success of dreissenid mussels as invasive species.  相似文献   

Numerical Modeling and Observations of Tsunami Waves in Alberni Inlet and Barkley Sound, British Columbia     

Isaac V. Fine  Josef Y. Cherniawsky  Alexander B. Rabinovich  Fred Stephenson 《Pure and Applied Geophysics》2008,165(11-12):2019-2044

Alberni Inlet is a long and narrow fjord adjacent to Barkley Sound on the Pacific Coast of Vancouver Island, Canada. Port Alberni, at the head of the inlet, was affected in 1964 by the largest Pacific tsunami waves in Canadian history. We use observations and results from two numerical models to investigate the resonant characteristics of the region and amplification of tsunami waves in Barkley Sound and Alberni Inlet. The first model (A) was forced at its open boundary with a stationary autoregressive signal, similar to the observed background noise. The second model (B) used an initial sea-level deformation from a potential earthquake off California in the southern segment of the Cascadia Subduction Zone, producing transient tsunami waves. Spectral, cross-spectral and frequency-time (f-t) analyses of the observations were used to examine the resonant properties and topographic response of the local area. The respective results show large admittance functions over a wide 0.5–0.9 cph frequency band, implying a low Q factor but high amplification of arriving waves. This unusual behavior is a result of two effects: A quarter-wave resonance of the system for its fundamental Helmholtz mode and amplification due to the narrowing of the channel cross section from Barkley Sound to Alberni Inlet. The model A numerical results agree favorably with the observations, indicating an energetic resonant mode at frequency of ~0.53 cph (112 min), with its nodal line located near the entrance to Barkley Sound and amplification factor value close to 12. The results from the tsunami propagation model (B) yield spectral characteristics similar to those from the model A and from the observations. The maximum tsunami current speed for this scenario is 2.4 ms^?1 in Sproat Narrows, which divides Alberni Inlet into two parts, while the largest computed wave height is 1.6 m in the northern Alberni Inlet, in the area of Port Alberni.  相似文献   

从极化区的功能探讨长江三角洲的扩展范围   总被引：3，自引：0，他引：3  

段学军  虞孝感  Josef Nipper 《地理学报》2009,64(2)

极化区作为一种具有全球意义的区域发展模式和空间组合形式,日益成为集聚经济要素和支配国家乃至全球经济命脉的巨大载体,承担着引领国家经济发展、参与世界竞争的功能.长江三角洲地区经过了近30年的高速发展,已经初具极化区的特征.但是,与其它世界级极化区相比,长江三角洲地区整体实力和带动能力仍然不足,国际竞争力还很有限.通过扩展极化区范围,可以扩大长江三角洲核心地区的腹地,缓解极化区资源环境瓶颈约束.关于长江三角洲地区的合理范围,各界意见纷纭,争论较多.基于"长三角"作为世界极化区的要求,从极化氏的科学概念、条件和以提高国际竞争力、完善极化区功能的目标出发,通过区域内城市之间的功能互补和经济联系分析,结合区域一体化的现实性,研究了扩大"长三角"的合理范围,得出了应把温州、金华、盐城、淮安、马鞍山、芜湖、铜陵、巢湖、合肥、滁州、宣城等城市作为扩展优先选择区,把宿迁、徐州、连云港、丽水、衢州、池州、安庆、蚌埠、黄山、宿州等城市作为扩展保留资格区,从而把长江三角洲地区从16个城市逐步扩大到37个城市的结论.  相似文献