Changing rainfall inputs in the Volta basin: implications for water sharing in Ghana     

Kwadwo Owusu  Peter Waylen  Youliang Qiu 《GeoJournal》2008,71(4):201-210

We present evidence from the analysis of gridded annual rainfall data that, increased variability and declining rainfall totals are the main cause of declining lake levels in the Volta basin above the Akosombo Dam. West Africa has undergone a period of diminished rainfall, punctuated by a series of severe droughts and marked by a shift in rainfall regime. As a result, lake levels behind the hydro-electric impoundment have fluctuated so widely at times that, power has had to be rationed. The trends in the spatial and temporal variability of annual rainfall in the riparian nations explain the low impoundment levels frequent in recent decades. The drying of Burkina Faso and Mali is particularly marked and synchronous to an apparent shift in the rainfall regime in Ghana towards a longer dry season and vanishing short dry spell, the effects which tend to negate each other. The various regional and temporal associations between El Niño-Southern Oscillation phenomenon (ENSO) are investigated as a possible cause of variation across the basin. The strengths of these associations and low frequency shifts suggest an unfortunate correspondence between national and climatological boundaries which may serve to heighten regional political tensions resulting from ENSO effects. Lack of re-investment in the Akosombo Dam as a result of management policies, political and pre-construction contractual agreements have all conspired in recent decades to make these hydro-climatological changes more devastating.  相似文献   

Natural hazards in Australia: droughts   总被引：3，自引：0，他引：3  

Anthony S. Kiem  Fiona Johnson  Seth Westra  Albert van Dijk  Jason P. Evans  Alison O’Donnell  Alexandra Rouillard  Cameron Barr  Jonathan Tyler  Mark Thyer  Doerte Jakob  Fitsum Woldemeskel  Bellie Sivakumar  Raj Mehrotra 《Climatic change》2016,139(1):37-54

  相似文献   

Natural hazards in Australia: floods     

Fiona Johnson  Christopher J. White  Albert van Dijk  Marie Ekstrom  Jason P. Evans  Dörte Jakob  Anthony S. Kiem  Michael Leonard  Alexandra Rouillard  Seth Westra 《Climatic change》2016,139(1):21-35

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Facilitating linkage of climate policies through the Paris outcome   总被引：1，自引：1，他引：0  

Daniel M. Bodansky  Seth A. Hoedl  Robert N. Stavins 《Climate Policy》2016,16(8):956-972

The Durban Platform for Enhanced Action negotiations are likely to lead to a Paris outcome that embodies a hybrid climate policy architecture, combining top-down elements, such as for monitoring, reporting, and verification, with bottom-up elements, including ‘Intended Nationally Determined Contributions’ from participating countries, detailing plans to reduce emissions, based on national circumstances. For such a system to be cost-effective – and thus more likely to embody greater ambition – a key feature will be linkages among regional, national, and sub-national climate policies. By linkage, we mean formal recognition by a mitigation programme in one jurisdiction of emission reductions undertaken in another jurisdiction for the purposes of complying with the first jurisdiction's requirements. The Paris outcome could play at least four different roles with respect to linkage of heterogeneous policy instruments. First, it could discourage linkage, either by not allowing countries to count international transfers toward their mitigation contributions, or by limiting the number or types of transferred units that can be counted for compliance purposes. Second, it could be silent on the topic of linkage, creating legal and regulatory uncertainty about whether international transfers are allowed. Third, it could expressly authorize linkage but not provide any further details about how linkage should occur, leaving it to future United Nations Framework Convention on Climate Change negotiating sessions to work out the details or to national governments to develop bilateral or multilateral linkage arrangements. Finally, the Paris outcome could establish institutional arrangements and rules that facilitate and promote linkage. We examine how a future international policy architecture could help facilitate the growth and operation of a robust system of international linkages. Several design elements merit serious consideration for inclusion in the Paris outcome, either in the core agreement or by establishing a process for subsequent international elaboration. At the same time, including detailed linkage rules in the core agreement is not desirable because this could make it difficult for rules to evolve in light of experience.

Policy relevance

These findings have implications for the efficient and effective design of an international climate policy architecture by detailing the role that linkage can play in supporting heterogeneous climate policies at the regional, national, and sub-national levels.  相似文献   

Efficient solution for matrix-fracture flow with multiple interacting continua     

Edward H. Smith  Mohan S. Seth 《国际地质力学数值与分析法杂志》1999,23(5):427-438

An efficient numerical procedure for implementing the multiple interacting continua (MINC) method for fractured porous media in a general-purpose multiphase simulator is presented. This procedure is substantially faster, requires less memory, is amenable to any n-component, multiphase non-isothermal package, and is readily adaptable for parallel processing computers. The present procedure results in a reduction of the computing time by a factor of the order of NMINC³ as compared to the band algorithm, where NMINC is the number of nested continua into which each matrix block is further discretized. The memory requirement approaches a reduction factor of the order of NMINC² for larger problems compared to the band algorithm. The code for the algorithm was structured so as to set up the time consuming, but independent, computations for each matrix block in a subroutine that was parallelized and tested using a Sequent machine accessed under a UNIX environment. For NMINC=10, total computing time was reduced by 33 per cent for the use of two versus one processor, with the savings increasing for increasing NMINC. The proposed procedure can be implemented with the same ease and efficiency in conjunction with any iterative or direct method, and the grid-blocks can be ordered in any non-standard manner such as in D-4, D-2, and others. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Evaluating social vulnerability indicators: criteria and their application to the Social Vulnerability Index     

Spielman  Seth E.  Tuccillo  Joseph  Folch  David C.  Schweikert  Amy  Davies  Rebecca  Wood  Nathan  Tate  Eric 《Natural Hazards》2020,100(1):417-436

Natural Hazards - As a concept, social vulnerability describes combinations of social, cultural, economic, political, and institutional processes that shape socioeconomic differentials in the...  相似文献   

大陆内的长余震序列和对地震危险性评估的意义   总被引：3，自引：0，他引：3  

Seth Stein  刘勉  杨雅琼 《世界地震译丛》2009,(4):1-6

板块构造学说最强大的特点之一,是通过已知的板块运动可以了解板块边界未来大地震的地点和平均复发间隔。然而板块构造学却不能探知板块之内何时何处发生地震,因为理想的板块内部不发生形变。因此,在板块内部,进行地震危险性评估主要依靠的假设是,短期历史记录给出的小地震的位置反映出连续形变从而引发未来大地震（Shed—locketal,2000）。然而在此我们提出,最近的这些地震有许多可能是数百年前大地震的余震。我们提出一简单模型可预测：余震序列的长度和断层应力加载的速．率成反比。  相似文献   

大陆内部长余震序列及其对地震风险评估的启示     

Seth Stein  Mian Liu  刘杨  朱守彪 《国际地震动态》2009,(12):7-12

板块构造学说的最有力的特征之一,是已知的板块运动让我们对板块边界未来大地震的发震位置和平均复发间隔有更清晰的认识。然而,板块构造学说却不能预测板块内的地震何时何地发生,因为理想的板块内部是不会变形的。因此,板块内部的地震风险评估过于依靠如下假设：从有限的历史记录中得到的小地震发震位置能够反映出连续变形的地区,而变形将诱发未来大地震[1]。然而,本文将要说明的是,最近许多这样的小地震很可能是几百年前发生过的大地震的余震。文中将给出一个简单的模型,并由此模型得出：余震序列的长度和断层加载速率呈反比关系。发生在缓慢变形的大陆内部的余震序列,其持续时间与在快速加载的板块边界所观测到的典型的10年尺度余震序列相比要长得多。因为这些预测与观测结果相符,所以将大陆内部地震看作稳态地震活动的一般做法高估了目前地震活跃地区的地震危险性,而低估了其他地区的地震风险。  相似文献   

Differential developmental toxicity of naphthoic acid isomers in medaka (Oryzias latipes) embryos     

Carney MW  Erwin K  Hardman R  Yuen B  Volz DC  Hinton DE  Kullman SW 《Marine pollution bulletin》2008,57(6-12):255-266

Polycyclic aromatic hydrocarbons (PAHs) are widespread persistent pollutants that readily undergo biotic and abiotic conversion to numerous transformation products in rivers, lakes and estuarine sediments. Here we characterize the developmental toxicity of four PAH transformation products each structural isomers of hydroxynaphthoic acid: 1H2NA, 2H1NA, 2H3NA, and 6H2NA. Medaka fish (Oryzias latipes) embryos and eleutheroembryos were used to determine toxicity. A 96-well micro-plate format was used to establish a robust, statistically significant platform for assessment of early life stages. Individual naphthoic acid isomers demonstrated a rank order of toxicity with 1H2NA>2H1NA>2H3NA>6H2NA being more toxic. Abnormalities of circulatory system were most pronounced including pericardial edema and tube heart. To determine if HNA isomers were AhR ligands, spatial-temporal expression and activity of CYP1A was measured via in vivo EROD assessments. qPCR measurement of CYP1A induction proved different between isomers dosed at respective concentrations affecting 50% of exposed individuals (EC50s). In vitro, all ANH isomers transactivated mouse AhR using a medaka CYP1A promoter specific reporter assay. Circulatory abnormalities followed P450 induction and response was consistent with PAH toxicity. A 96-well micro-plates proved suitable as exposure chambers and provided statistically sound evaluations as well as efficient toxicity screens. Our results demonstrate the use of medaka embryos for toxicity analysis thereby achieving REACH objectives for the reduction of adult animal testing in toxicity evaluations.  相似文献   

Dynamics of rotationally fissioned asteroids: Source of observed small asteroid systems     

Seth A. Jacobson  Daniel J. Scheeres 《Icarus》2011,214(1):161-178

We present a model of near-Earth asteroid (NEA) rotational fission and ensuing dynamics that describes the creation of synchronous binaries and all other observed NEA systems including: doubly synchronous binaries, high-e binaries, ternary systems, and contact binaries. Our model only presupposes the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect, “rubble pile” asteroid geophysics, and gravitational interactions. The YORP effect torques a “rubble pile” asteroid until the asteroid reaches its fission spin limit and the components enter orbit about each other (Scheeres, D.J. [2007]. Icarus 189, 370-385). Non-spherical gravitational potentials couple the spin states to the orbit state and chaotically drive the system towards the observed asteroid classes along two evolutionary tracks primarily distinguished by mass ratio. Related to this is a new binary process termed secondary fission - the secondary asteroid of the binary system is rotationally accelerated via gravitational torques until it fissions, thus creating a chaotic ternary system. The initially chaotic binary can be stabilized to create a synchronous binary by components of the fissioned secondary asteroid impacting the primary asteroid, solar gravitational perturbations, and mutual body tides. These results emphasize the importance of the initial component size distribution and configuration within the parent asteroid. NEAs may go through multiple binary cycles and many YORP-induced rotational fissions during their approximately 10 Myr lifetime in the inner Solar System. Rotational fission and the ensuing dynamics are responsible for all NEA systems including the most commonly observed synchronous binaries.  相似文献