West Antarctica's sensitivity to natural and human‐forced climate change over the Holocene     

P. A. Mayewski  K. A. Maasch  D. Dixon  S. B. Sneed  R. Oglesby  E. Korotkikh  M. Potocki  B. Grigholm  K. Kreutz  A. V. Kurbatov  N. Spaulding  J. C. Stager  K. C. Taylor  E. J. Steig  J. White  N. A. N. Bertler  I. Goodwin  J. C. Simões  R. Jaña  S. Kraus  J. Fastook 《第四纪科学杂志》2013,28(1):40-48

The location and intensity of the austral westerlies strongly influence southern hemisphere precipitation and heat transport with consequences for human society and ecosystems. With future warming, global climate models project increased aridity in southern mid‐latitudes related to continued poleward contraction of the austral westerlies. We utilize Antarctic ice cores to investigate past and to set the stage for the prediction of future behaviour of the westerlies. We show that Holocene West Antarctic ice core reconstructions of atmospheric circulation sensitively record naturally forced progressive as well as abrupt changes. We also show that recent poleward migration of the westerlies coincident with increased emission of greenhouse gases and the Antarctic ozone hole has led to unprecedented penetration, compared with >100,000 years ago, of air masses bringing warmth, extra‐Antarctic source dust and anthropogenic pollutants into West Antarctica. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Non‐Matrix‐Matched Calibration for the Multi‐Element Analysis of Geological and Environmental Samples Using 200 nm Femtosecond LA‐ICP‐MS: A Comparison with Nanosecond Lasers     

Klaus Peter Jochum  Brigitte Stoll  Ulrike Weis  Dorrit E. Jacob  Regina Mertz‐Kraus  Meinrat O. Andreae 《Geostandards and Geoanalytical Research》2014,38(3):265-292

LA‐ICP‐MS is one of the most promising techniques for in situ analysis of geological and environmental samples. However, there are some limitations with respect to measurement accuracy, in particular for volatile and siderophile/chalcophile elements, when using non‐matrix‐matched calibration. We therefore investigated matrix‐related effects with a new 200 nm femtosecond (fs) laser ablation system (NWRFemto200) using reference materials with different matrices and spot sizes from 10 to 55 μm. We also performed similar experiments with two nanosecond (ns) lasers, a 193 nm excimer (ESI NWR 193) and a 213 nm Nd:YAG (NWR UP‐213) laser. The ion intensity of the 200 nm fs laser ablation was much lower than that of the 213 nm Nd:YAG laser, because the ablation rate was a factor of about 30 lower. Our experiments did not show significant matrix dependency with the 200 nm fs laser. Therefore, a non‐matrix‐matched calibration for the multi‐element analysis of quite different matrices could be performed. This is demonstrated with analytical results from twenty‐two international synthetic silicate glass, geological glass, mineral, phosphate and carbonate reference materials. Calibration was performed with the certified NIST SRM 610 glass, exclusively. Within overall analytical uncertainties, the 200 nm fs LA‐ICP‐MS data agreed with available reference values.  相似文献   

Development of a Matrix‐Matched Sphalerite Reference Material (MUL‐ZnS‐1) for Calibration of In Situ Trace Element Measurements by Laser Ablation‐Inductively Coupled Plasma‐Mass Spectrometry          下载免费PDF全文

Peter Onuk  Frank Melcher  Regina Mertz‐Kraus  Hans‐Eike Gäbler  Simon Goldmann 《Geostandards and Geoanalytical Research》2017,41(2):263-272

Sphalerite (ZnS) is an abundant ore mineral and an important carrier of elements such as Ge, Ga and In used in high‐technology applications. In situ measurements of trace elements in natural sphalerite samples using LA‐ICP‐MS are hampered by a lack of homogenous matrix‐matched sulfide reference materials available for calibration. The preparation of the MUL‐ZnS1 calibration material containing the trace elements V, Cr, Mn, Co, Ni, Cu, Ga, Ge, As, Se, Mo, Ag, Cd, In, Sn, Sb, Tl and Pb besides Zn, Fe and S is reported. Commercially available ZnS, FeS, CdS products were used as the major components, whereas the trace elements were added by doping with single‐element ICP‐MS standard solutions and natural mineral powders. The resulting powder mixture was pressed to pellets and sintered at 400 °C for 100 h using argon as an inert gas. To confirm the homogeneity of major and trace element distributions within the MUL‐ZnS1 calibration material, measurements were performed using EPMA, solution ICP‐MS, ICP‐OES and LA‐ICP‐MS. The results show that MUL‐ZnS‐1 is an appropriate material for calibrating trace element determination in sphalerite using LA‐ICP‐MS.  相似文献   

VSOP observations of the BL Lac object 2007+777     

C. Jin  T.P. Krichbaum  A. Witzel  R. Nan  B. Peng  A. Kraus  A. Lobanov  S. Qian  J.A. Zensus 《Astrophysics and Space Science》2001,277(1-2):97-100

A numerical model of magnetic turbulence allows us to compute the diffusion coefficients for different degrees of anisotropy, and in particular for the cases corresponding to the solar wind. We consider here the problem of the propagation of the energetic particles accelerated by corotating interaction regions (CIRs) and observed by Ulysses at high heliographic latitudes. The excursion in latitude of a magnetic field line located at large heliospheric distance is evaluated with a Monte Carlo simulation. In the calculations, the random `force' terms are proportional to the square root of the diffusion coefficient in each direction. By tracing a large number of field lines, we can devise how the particles would be seen by Ulysses. Good agreement with the actual observations is found. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Actinic Radiation and Photolysis Processes in the Lower Troposphere: Effect of Clouds and Aerosols     

W. Junkermann  C. Brühl  D. Perner  E. Eckstein  T. Trautmann  B. Früh  R. Dlugi  T. Gori  A. Ruggaber  J. Reuder  M. Zelger  A. Hofzumahaus  A. Kraus  F. Rohrer  D. Brüning  G. Moortgat  A. Horowitz  J. Tadić 《Journal of Atmospheric Chemistry》2002,42(1):413-441

Within the German Tropospheric Research Program (TFS) a series of projects were performed focussing on aspects of radiation transfer and the effects of UV-radiation on air chemistry. The individual projects covered laboratory investigations, instrument development for photolysis processes as well as field studies of actinic radiation and comparison to model calculations. One and three-dimensional models were tested against field campaign data. The results confirm the improvement of measurement technology achieved through deployment of new techniques like spectroradiometry that offer a wider range of investigations than was previously attainable using chemical actinometry or fixed wavelength filter radiometry. Reasonable agreement was also found between measurements and models for a few selected and well defined cloudy conditions. On the other hand, using simple stratiform geometry models yielded significant deviations between measurement and model in both directions particularly in the case of high zenith angles and with high aerosol load. Further tools both for experimental investigations and for model calculations were developed within the framework of the Troposphere Research Program (TFS) and deficiencies were identified demanding further investigations when broken clouds and more complex cloud layers prevail.  相似文献   

Enhanced cold front propagation due to turbulent mixing     

A. Becker  K. Keuler  C. M. Ewenz  H. Kraus  E. Schaller 《Meteorology and Atmospheric Physics》1997,62(3-4):201-214

Summary The influence of turbulent friction on the propagation of cold fronts is investigated by numerical simulations using a two-dimensional mesoscale model. We compare the frictional effect with the effects of large-scale shear forcing and energy conversion at the earth's surface and discuss the synergic effect of all three mentioned processes. There is no pure superposition of these effects indicating that nonlinear interaction plays a role. In addition it is possible to show that—depending on the along-front jet—friction does not necessarily slow down the front but can also accelerate it. The direction of the along-front jet within the planetary boundary layer (PBL) is crucial for that question.With 12 Figures  相似文献   

Turbulence frontogenesis     

Prof. Dr. H. Kraus 《Meteorology and Atmospheric Physics》1992,48(1-4):309-315

Summary The frontogenesis function in terms of the time derivative of the gradient of any relevant airborne quantity comprises all processes contributing to frontogenesis. Thus the various terms of this function are able to reveal processes of frontal development and their structure. Therefore the evaluation of these terms from measurements or in the frame of model simulations offers the chance of gaining more insight in frontal processes. If frontogenesis is evaluated from average basic data representative for a certain time-or space-scale, the result will be a kind of average frontogenesis, which naturally contains turbulence terms in the form of covariances. The processes described by these terms are called turbulence frontogenesis.This paper describes the basic formalisms of turbulence frontogenesis, offers cross-sections of these terms gained in experiments flown in sea-breeze fronts and gives some hints about their general behaviour.With 4 Figures  相似文献   

Correction of data from a salt-spray contaminated temperature sensor     

Jörg Hartmann  Jörg Hacker  Helmut Kraus 《Boundary-Layer Meteorology》1990,50(1-4):153-169

Sea salt spray contamination of a temperature sensor induces erroneous fluctuations due to the latent heat of evaporating or condensing water vapour associated with changes in humidity. A method is derived to correct this humidity sensitivity using data from a fast response humidiometer. When applied to aircraft measurements of turbulence in the mixed layer over the Coral Sea, spurious high frequency temperature variance is significantly corrected. Spatial separation of the thermometer and the humidiometer and the sampling rate limit the effectiveness of the method. The vertical profile of the structure function parameter C _T ², determined from the corrected data, agrees well with results from other studies in a marine environment, but differences with measurements made over land remain.  相似文献   

Atmospheric boundary layer characteristics in severe smog episodes     

Prof. H. Kraus  U. Ebel 《Meteorology and Atmospheric Physics》1989,40(4):211-224

Summary The article brings together theoretical knowledge about the structure of the atmospheric boundary layer (ABL) which should be typical for smog situations and ABL features observed during two severe smog episodes. It can be shown that the convective boundary layer (CBL) as a special ABL type is very favourable for the occurrence of smog and that at first glance simple modelling of the CBL seems to recommend itself for forecasting purposes.However, the real smog situations show much more complexity, and even high reaching (up to 1500 m) stable boundary layers (SBL) occur. Simple modelling fails because important input parameters (such as vertical wind and advection terms) cannot be derived neither from measurements nor from meso-scale models in sufficient accuracy. Even the most advanced forecast models cannot describe the ABL structure correctly or in sufficient detail to estimate the development of a smog situation.With 19 Figures  相似文献   

Die Alpen als Doppelorogen     

E. Kraus 《International Journal of Earth Sciences》1931,22(2):65-78

Zusammenfassung Unter Orogen verstehen wir die regionalgenetische Einheit der geosynklinalen Struktur. Diese Einheit wird durch die Existenz einer Verschluckungszone gegeben, gegen welche hin oft spiegelbildlich von beiden Seiten die Massen unter Sedimentverdickung, dann Faltung, Überschiebung angesaugt worden sind. Das Orogen ist darum typischerweise zweiseitig mit abtauchender Bewegungsstruktur gegen innen. Ganz symmetrisch finden wir es aber selten oder nie, weil offenbar der Abstrom nicht genau senkrecht nach unten, sondern im allgemeinen schräg nach unten erfolgte. Es ist auch oft in seiner Zweiseitigkeit nicht zu erkennen, weil große Teile, ganze Flanken, niedergebrochen sind, unter jüngeren Sedimenten oder unter dem Meer versanken.Die Alpen sind ein Sonderfall, in dem zwei Orogene oder Narbenzonen nahe aneinandertreten und einander immer wieder beeinflußt haben. Durch das Übermächtigwerden des südalpinen Narbenabstroms in den Westalpen wurde die benachbarte Nordnarbe mit ihrem ganzen Bau völlig überwältigt, ausgeschaltet, wurden die dinarischen Massen der Südflanke so gewaltig versenkt, daß sie unter der Po-Ebene verschwanden. Nicht nur die unvergleichlichen Durchbewegungen und Massentransporte der Westalpen, auch die Einkrümmung des westalpinen Bogens um diesen Wirbel abnorm gesteigerter Absaugung herum und wohl auch die Bildung der großen, nordwestlich anschließenden Zerrungsgräben sind Folgen solcher Dynamik. Sie hat den Hauptteil der Alpen zu der höheren Einheit eines Doppelorogens zusammengeschweißt.  相似文献