Lesson from the past: present insolation minimum holds potential for glacial inception     

Ulrich C. Müller  Jrg Pross 《Quaternary Science Reviews》2007,26(25-28):3025-3029

The community of climatologists predicts a progressive global warming [IPCC Fourth Assessment Report—Climate Change, 2007. The Scientific Basis. Cambridge University Press, Cambridge] that will not be interrupted by a glacial inception for the next 50 ka [Berger and Loutre, 2002. An exceptionally long Interglacial ahead? Science 297, 1287–1288]. These predictions are based on continuously increasing anthropogenic greenhouse gas emissions and on the orbital forcing that will provide only muted insolation variations for the next 50 ka. To assess the potential climate development without human interference, we analyse climate proxy records from Europe and the North Atlantic of Marine Isotope Stage (MIS) 11 (423–362 ka BP), an interval when insolation variations show a strong linear correlation with those of the recent past and the future. This analysis suggests that the insolation minimum at 397 ka BP, which provides the best available analogue to the present insolation minimum, terminated interglacial conditions in Europe. At that time, tundra–steppe vegetation spread in Central Europe and pine forests dominated in the eastern Mediterranean region. Because the intensities of the 397 ka BP and present insolation minima are very similar, we conclude that under natural boundary conditions the present insolation minimum holds the potential to terminate the Holocene interglacial. Our findings support the Ruddiman hypothesis [Ruddiman, W., 2003. The Anthropogenic Greenhouse Era began thousands of years ago. Climate Change 61, 261–293], which proposes that early anthropogenic greenhouse gas emission prevented the inception of a glacial that would otherwise already have started.  相似文献   

Motoji Ikeya (1940–2006)     

Rainer Grün  Ulrich Radtke  Richard G. Roberts 《Quaternary Geochronology》2007,2(1-4):2-3

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Electrical Monitoring of In Situ Chemical Oxidation by Permanganate     

Lisa Cavé  Niels Hartog  Tom Al  Beth Parker  K. Ulrich Mayer  Steven Cogswell 《Ground Water Monitoring & Remediation》2007,27(2):77-84

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Magnetic mapping for the detection and characterization of UXO: Use of multi-sensor fluxgate 3-axis magnetometers and methods of interpretation   总被引：1，自引：0，他引：1  

Marc Munschy  Daniel Boulanger  Patrice Ulrich  Mustapha Bouiflane 《Journal of Applied Geophysics》2007,61(3-4):168-183

Fluxgate vector magnetometers can be powerful instruments in magnetic mapping and in the detection of unexploded ordnance (UXO). Being lightweight and having low power requirements, they allow the development of multi-sensor use. The main problems in using fluxgate magnetometers arise from calibration errors and drift but these can be overcome using a quick and simple method of calibration in the field. This method also has the advantage of compensating permanent and induced magnetic fields generated by magnetized objects carried with the sensors. Measurement accuracy is similar to that obtained with scalar magnetometers. Multi-magnetometer profiling allows direct inversion of raw magnetic data along profiles in order to locate and characterize dipoles typically generated by UXO. The method used is a non-linear inverse procedure that estimates the three coordinates and magnetization vector of the dipole. Application of the technique to both a synthetic case and a field example illustrates the advantages of the method compared with the use of the analytic signal.  相似文献   

Reviews     

Peter R. Odell  Seiya Uyeda  V. P. Zenkovich  C. Koeman  Johannes Ulrich  Maurice K.-Seguin  K. Gerke  U. Vetter  G. T. W. Wittmann  H. J. Habing  J. Gentilli 《GeoJournal》1980,1(1):95-100

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Low-Degree Low-Order Solar p Modes As Seen By GOLF On board SOHO     

GarcÍa  R.A.  Régulo  C.  Turck-Chièze  S.  Bertello  L.  Kosovichev  A.G.  Brun  A.S.  Couvidat  S.  Henney  C.J.  Lazrek  M.  Ulrich  R.K.  Varadi  F. 《Solar physics》2001,200(1-2):361-379

Data recovered from the GOLF experiment on board the ESA/NASA SOHO spacecraft have been used to analyze the low-order low-degree solar velocity acoustic-mode spectrum below =1.5 mHz (i.e., 1n9,l2). Various techniques (periodogram, RLAvCS, homomorphic-deconvolution and RLSCSA) have been used and compared to avoid possible biases due to a given analysis method. In this work, the acoustic resonance modes sensitive to the solar central region are studied. Comparing results from the different analysis techniques, 10 modes below 1.5 mHz have been identified.  相似文献   

Behaviour Of An Ultrasonic Anemometer Under Cloudy Conditions     

Holger Siebert  Ulrich Teichmann 《Boundary-Layer Meteorology》2000,94(1):165-169

The use of ultrasonic anemometers under cloudy weather conditions is often doubted, even rejected or not discussed in the literature. To investigate the influence of liquid water content on the behaviour of sonic anemometers a small intercomparison experiment using an ultrasonic anemometer, a fast response propeller anemometer, and a Particulate Volume Monitor was performed at the German Environmental Research Station Schneefernerhaus near the top of Mt. Zugspitze. The results obtained under different conditions (dry/cloudy) give no significant hint on such an influence.  相似文献   

Genesis Conditions for Thunderstorm Growth and the Development of a Squall Line in the Northern Alpine Foreland     

M. Peristeri  W. Ulrich  R. K. Smith 《Meteorology and Atmospheric Physics》2000,72(2-4):251-260

Summary  Two numerical models are used to investigate aspects of thunderstorm dynamics and thunderstorm initiation in the northern Alpine foreland. The first, an isentropic model of airflow over and around the Alps, is used to investigate flow patterns favourable for the initiation of deep convection in the region. It is found that a stably-stratified southerly flow towards the Alps leads to a southwesterly flow in the Alpine foreland, a situation most often found during thunderstorm periods, and to the formation of a gravity wave in the lee of the Alps. This wave is accompanied by raised isentropes which, in reality, would lead to a reduction in static stability and convective inhibition as well as an increase in convective available potential energy. The second model, a cloud model, is used to study the development of an observed squall line over southern Bavaria. The model is initialized with wind, temperature and moisture profiles from a radiosonde sounding ahead of the squall line and the squall line is initiated by an array of thermal bubbles. The model simulation is used to interpret the evolution of the squall line. Received March 9, 1999/Revised July 10, 1999  相似文献   

A fully implicit model for simulating dynamo action in a Cartesian domain     

Jrg Schmalzl  Ulrich Hansen 《Physics of the Earth and Planetary Interiors》2000,120(4):458-349

We present a fully implicit numerical method to solve the incompressible MHD equations in a strongly rotating Cartesian domain. The equations are solved in a primitive variable formulation using a finite volume discretization. In order to use massively parallel computers, we applied a domain decomposition approach in space. The performance of this model is compared with an earlier model, which treated the convective terms of the equations in an explicit manner. Our results indicate that although the fully implicit method needs about three times the memory of the implicit–explicit method, it is superior in terms of computational efficiency. As an application of this model, we investigated the influence of the Prandtl number in the range of 0.01–1000 on the dynamics of the dynamo.  相似文献   

Depletion of a brine layer at the base of ridge-crest hydrothermal systems     

Stan Schoofs  Ulrich Hansen 《Earth and Planetary Science Letters》2000,180(3-4):341-353

The variable salinity of fluid venting from mid-ocean ridges is indicative of mixing between hydrothermal seawater and fluids that have undergone supercritical phase separation. In order to study the stability of a brine-saturated layer that may form in the lowermost part of the hydrothermal system, we have performed numerical simulations of a system that has returned into the subcritical regime. For typical geological parameters, it is shown that the interface between the brine layer and the overlying fluids is not very stable, but vanishes by one of two dynamical mechanisms: convective breakdown or vertical migration. This contradicts the conventional picture of a steady, layered convective system in which the brine is depleted only by dispersion and diffusion across the interface. The depletion mechanism depends on the fluid-dynamical stability of the brine layer. Convection within the brine layer results either in the convective breakdown (for low excess salinity of the brine, as compared to seawater) or the upward migration of the interface (for higher excess salinities). Consequently, the depletion times are much shorter than for models with pure dispersion/diffusion across the interface. If the brine layer is static, high-chlorinity liquid is entrained slowly by the convecting overlying fluids, leading to downward migration of the interface. This gradual depletion of the brine layer results in almost constant vent salinities, in agreement with measured salinities of chronic high-chlorinity vents.  相似文献