The behavior of jet streams in potential fallout situations     

Prof. Dr. Elmar R. Reiter 《Meteorology and Atmospheric Physics》1968,17(1):8-16

Summary It is shown from a case study that the splitting of jet streams into several branches, which is frequently observed over the United States on the leading edges of intense maxima, may be explained by conservation of potential vorticity within an atmospheric layer moving over an obstacle. Such an obstacle may be a large mountain barrier, such as the Rocky Mountains, or a slowmoving dome of cold air in the lower troposphere, as is typical for cold outbreaks associated with strong jet streams.

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Zusammenfassung An Hand eines konkreten Falles wird gezeigt, daß die Aufspaltung des Jet Streams in mehrere Äste, wie dies häufig über den Vereinigten Staaten an der Vorderseite intensiver Jet Maxima beobachtet wird, mit der Erhaltung der potentiellen Vorticity innerhalb einer Luftschicht, die sich über ein Hindernis bewegt, erklärt werden kann. Ein derartiges Hindernis kann einerseits durch ein Gebirge gegeben sein, wie etwa die Rocky Mountains, andererseits aber auch durch eine sich nur langsam fortbewegende Kaltluftmasse in der unteren Troposphäre. Eine solche ist für Kaltluftausbrüche im Zusammenhang mit intensiven Strahlströmen charakteristisch.

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Résumé En se basant sur un cas particulier, on montre que la subdivision d'un courant jet en plusieurs bras distincts — fait souvent observé au dessus des Etats Unis d'Amérique à l'avant de la zone d'intensité maximum — peut s'expliquer par la conservation de l'énergie tourbillonnaire potentielle d'une couche d'air se déplaçant sur un obstacle. Un tel obstacle peut être soit une importante chaîne de montagnes telles que les Rocheuses, soit une masse d'air froid se déplaçant lentement dans la basse troposphère, comme c'est typiquement le cas lorsqu'une invasion d'air froid est liée à un fort courant jet.

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With 3 Figures  相似文献   

Shock-effects on the K-Ar system of plagioclase feldspar and the age of anorthosite inclusions from North-Eastern Minnesota   总被引：1，自引：0，他引：1  

Elmar K Jessberger  Rolf Ostertag 《Geochimica et cosmochimica acta》1982,46(8):1465-1471

Artificial shock pressures up to 52.5 GPa have no influence on the K-Ar system of plagioclase feldspar. The ⁴⁰Ar-³⁹Ar analysis of feldspar (labradorite An₆₇ from anorthosite of North-Eastern Minnesota) shocked up to 45 GPa—in vacuo, to prevent massive entrapment of atmospheric argon-shows that the age spectra and the argon diffusion properties remain unaltered. Similar feldspar samples (labradorite An₅₁ from Nain, Labrador), shocked in air up to 52.5 GPa and dated by the conventional K-Ar method, also yield the same age as unshocked samples but with a higher atmospheric argon contribution. The Minnesota anorthosite has an ⁴⁰Ar-³⁹Ar age of 1075 ± 10 m.y. No information on a possible previous history of the anorthosite became apparent.  相似文献   

Implications of weak near-term climate policies on long-term mitigation pathways     

Gunnar?LudererEmail author  Christoph?Bertram  Katherine?Calvin  Enrica?De?Cian  Elmar?Kriegler 《Climatic change》2016,135(1):127-141

While the international community has agreed on the long-term target of limiting global warming to no more than 2 °C above pre-industrial levels, only a few concrete climate policies and measures to reduce greenhouse gas (GHG) emissions have been implemented. We use a set of three global integrated assessment models to analyze the implications of current climate policies on long-term mitigation targets. We define a weak-policy baseline scenario, which extrapolates the current policy environment by assuming that the global climate regime remains fragmented and that emission reduction efforts remain unambitious in most of the world’s regions. These scenarios clearly fall short of limiting warming to 2 °C. We investigate the cost and achievability of the stabilization of atmospheric GHG concentrations at 450 ppm CO₂e by 2100, if countries follow the weak policy pathway until 2020 or 2030 before pursuing the long-term mitigation target with global cooperative action. We find that after a deferral of ambitious action the 450 ppm CO₂e is only achievable with a radical up-scaling of efforts after target adoption. This has severe effects on transformation pathways and exacerbates the challenges of climate stabilization, in particular for a delay of cooperative action until 2030. Specifically, reaching the target with weak near-term action implies (a) faster and more aggressive transformations of energy systems in the medium term, (b) more stranded investments in fossil-based capacities, (c) higher long-term mitigation costs and carbon prices and (d) stronger transitional economic impacts, rendering the political feasibility of such pathways questionable.  相似文献   

Loading fractures and Liesegang laminae: new sedimentary structures found in the north-western North Alpine Foreland Basin (Oligocene–Miocene, south-west Germany)     

John C. Tipper  Volker J. Sach†  Elmar P. J. Heizmann‡ 《Sedimentology》2003,50(4):791-813

Abstract Spectacular sedimentary structures recently found in the Molasse Basin (Oligocene–Miocene) in southern Germany were produced by soft‐sediment deformation under highly unusual conditions. These large, apparently wedge‐like structures –‘loading fractures’– cut down into beds of marl and are filled with coarse sand and intraclasts of shale. Wrapping the sides of the structures is a thin, continuous bed of layered dark claystone – the ‘DCB’. The upper and lower layers of this bed are an organic‐rich clay; the middle layer is a laminated quartzite. The precursor of the DCB was a lacustrine gyttja rich in diatom frustules. It was supersaturated in silica as it was buried. Subsequent diffusion of oxygen into this gyttja at a burial depth of only a few metres resulted in the formation of Liesegang laminae of quartz. These laminae grew and amalgamated, forming the layer of laminated quartzite. The sediments overlying the DCB were eventually removed by erosion, probably in a high‐energy marine environment. This erosion cut down to the DCB but was unable to penetrate it. The DCB remained exposed on the sea floor until a sudden depositional event occurred – the deposition of a 2·5 metre thick bed of coarse sand with shale intraclasts. Although the DCB had been able to resist the submarine erosion, it could not support the load of this new bed. The quartzite layer in it therefore fractured, transferring that load down onto the underlying, still‐unconsolidated marl. The intraclast‐rich sands were forced down into this marl, carrying ahead of them the partly broken remains of the DCB.  相似文献   

Risk Assessment of Vertical Breakwaters -A Case Study in Turkey   总被引：1，自引：2，他引：1  

CanElmarBALAS  LeventKOC 《中国海洋工程》2002,16(1):123-134

In the reliability-risk assessment, the second order reliability index (βⅡ ) method and the Conditional Expectation Monte Carlo (CEMC) simulation are interrelated as a new Level Ⅲ approach for the analysis of the safety level of the Dalaman yacht harbor vertical wall breakwater in Turkey. The missing wave data of the Dalaman measurement station are hindcasted by use of multi-layer feed-forward neural networks with the steepest descent and conjugate gradient algorithms. The structural failure probabilities of sliding and overturning failure modes are forecasted by approximation of the failure sur-face with a second-degree polynomial of an equal curvature at the design point. in the new approach, for each randomly generated load and tide combination, the joint failure probability reflects both the occurrence probability of loading condition and the structural failure risk at the limit state. The approach can be applied to risk assessment of vertical breakwaters in short CPU durations of portable comput  相似文献   

Surface analysis of stratospheric dust particles     

Detlef ROST  Thomas STEPHAN  Elmar K. JESSBERGER 《Meteoritics & planetary science》1999,34(4):637-646

Abstract— A controversially discussed and yet central question in interplanetary dust particle (IDP) research is the degree of alteration of these particles during their residence in the stratosphere. Especially, the typical enrichment of Br in chondritic IDPs (on the average ～21 × CI) has been inferred to be a result of contamination processes, probably invoking aerosol droplets. With time-of-flight secondary ion mass spectrometry (TOF-SIMS), we examined the surfaces of 13 stratospheric particles from the dust collector U2071. Six particles had severe, surface-bound, silicone oil residues preventing a proper analysis of their surfaces. Six other particles—-according to our scanning electron microscopy, energy dispersive x-ray spectrometer (SEM-EDS) studies preclassified as one (Fe,Ni)S-rich IDP, one Ca-rich particle, and four aluminum-oxide spheres—-carry the halogens F, Cl, and Br on the surface. At least for the aluminum-oxide spheres, we provide unequivocal evidence for a surface correlation of halogens. This evidence, taken together with that from previous studies, proves a general stratospheric contamination process which has to be considered in IDP research.  相似文献   

The Jebel Hadid structure (Al Kufrah Basin,SE Libya)—A possible impact structure and potential hydrocarbon trap?     

Martin Schmieder  Elmar Buchner  Daniel Paul Le Heron 《Marine and Petroleum Geology》2009

The Jebel Hadid structure that formed in the Nubian Sandstone of the southern Al Kufrah Basin is a ∼4.7 km circular feature with a set of multiple concentric annular ridges. The age of the structure is probably post-Early Cretaceous to pre-Pliocene. As the prevalent geological processes that usually account for the formation of circular structures (magmatism, diapirism, sand volcanism, karst dissolution, glacial erosion) can be widely excluded in this region, we suggest that the Jebel Hadid structure might represent an eroded, complex impact structure. In particular, the Jebel Hadid structure bears a strong morphological resemblance to the impact structure of Tin Bider in Algeria; general host rock properties may be compared to those at the Upheaval Dome impact structure, USA. Numerous terrestrial impact structures are hosts to hydrocarbon reservoirs. This investigation provides a first prospective approach based on remote sensing, discussing the economic potential of a circular structure of suspected impact origin. The still underexplored Al Kufrah Basin is considered as a high potential area for future hydrocarbon exploration. If we consider a possible impact origin of the Jebel Hadid structure, this feature might provide local secondary pathways and traps for hydrocarbon migration/accumulation in the Nubian Series and, thus, ought to be considered as a preferential site for oil and gas exploration.  相似文献   

Is atmospheric carbon dioxide removal a game changer for climate change mitigation?     

Elmar Kriegler  Ottmar Edenhofer  Lena Reuster  Gunnar Luderer  David Klein 《Climatic change》2013,118(1):45-57

The ability to directly remove carbon dioxide from the atmosphere allows the decoupling of emissions and emissions control in space and time. We ask the question whether this unique feature of carbon dioxide removal technologies fundamentally alters the dynamics of climate mitigation pathways. The analysis is performed in the coupled energy-economy-climate model ReMIND using the bioenergy with CCS route as an application of CDR technology. BECCS is arguably the least cost CDR option if biomass availability is not a strongly limiting factor. We compare mitigation pathways with and without BECCS to explore the impact of CDR technologies on the mitigation portfolio. Effects are most pronounced for stringent climate policies where BECCS is a key technology for the effectiveness of carbon pricing policies. The decoupling of emissions and emissions control allows prolonging the use of fossil fuels in sectors that are difficult to decarbonize, particularly in the transport sector. It also balances the distribution of mitigation costs across future generations. CDR is not a silver bullet technology. The largest part of emissions reductions continues to be provided by direct mitigation measures at the emissions source. The value of CDR lies in its flexibility to alleviate the most costly constraints on mitigating emissions.  相似文献   

A Carnian 40Ar/39Ar age for the Paasselkä impact structure (SE Finland)—An update          下载免费PDF全文

Winfried H. Schwarz  Martin Schmieder  Elmar Buchner  Mario Trieloff  Jarmo Moilanen  Teemu Öhman 《Meteoritics & planetary science》2015,50(1):135-140

A recrystallized band of pale feldspathic impact melt in a gneissic impact breccia from the approximately 10 km Paasselkä impact structure in southeast Finland was dated via ⁴⁰Ar/³⁹Ar step‐heating. The newly obtained plateau age of 228.7 ± 1.8 (2.2) Ma (2σ) (MSWD = 0.32; p = 0.93) is equal to the previously published pseudoplateau age of 228.7 ± 3.0 (3.4) (2σ) for the impact event. According to the current international chronostratigraphic chart and using the most recent published suggestions for the K decay constants, a Carnian (Late Triassic) age for the Paasselkä impact structure of 231.0 ± 1.8 (2.2) Ma (2σ) is calculated and considered the most precise and accurate age for this impact structure. The new plateau age for Paasselkä confirms the previous dating result but is, based on its internal statistics, much more compelling.  相似文献   

Book review     

Elmar R. Reiter 《Meteorology and Atmospheric Physics》1991,46(1-2):113-114

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