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101.
Jean-Louis Le Mouël Elena Blanter Mikhail Shnirman Vincent Courtillot 《Journal of Atmospheric and Solar》2009,71(12):1309-1321
Daily temperature and pressure series from 55 European meteorological stations covering the 20th century are analyzed. The overall temperature mean displays a sharp minimum near 1940 and a step-like jump near 1987. We evaluate the evolution of disturbances of these series using mean squared inter-annual variations and “lifetimes”. The decadal to secular evolutions of solar activity and temperature disturbances display similar signatures over the 20th century. Because of heterogeneity of the climate system response to solar forcing, regional and seasonal approaches are key to successful identification of these signatures. Most of the solar response is governed by the winter months, as best seen near the Atlantic Ocean. Intensities of disturbances vary by factors in excess of 2, underlining a role for the Sun as a significant forcing factor of European atmospheric variations. We speculate about the possible origin of these solar signatures. The last figure of the paper exemplifies its main results. 相似文献
102.
The current ammonite- and buchiid-based biostratigraphical successions of the Volgian Stage are outlined, with an analysis
of the most important data that support correlation throughout the Panboreal Superrealm. Updated ammonite zonal schemes were
proposed for the Volgian of the type region (the Russian Platform) and Svalbard. The lower Volgian successions in all areas
except the Russian Platform, with its eudemic virgatitid lineage and Submediterranean faunal elements, were dominated by Pectinatites and Eosphinctoceras-Subdichotomoceras. The last two genera were especially common eastwards from the Ural Mountains. During the middle Volgian, provincialism developed
quickly within the ammonites, and unified assemblages with early Palvovia and Dorsoplanites at the base of the substage were replaced by numerous local eudemic faunas. Despite this, migrations of species of Crendonites, Laugeites, Epivirgatites Epipallasiceras, Epilaugeites, and Taimyrosphinctes occurred at regular intervals and these enable precise correlations between the faunal sub-provinces. The zonation of the
upper Volgian is mainly based upon the succession of Craspedites (on Subcraspedites in England and North Sea), and can be traced throughout the Arctic. Zonation based on the bivalve Buchia enables correlations to be made between the successions over much of the Northern Hemisphere, including Northern California,
British Columbia, Arctic areas, and the Russian Platform. Each substage of the Volgian is characterized by buchiids with different
types of the ontogenetic development. Research on the infrazonal subdivision of the Volgian Stage based on buchiids is currently
in progress. Our analyses of the ammonite and buchiid successions of the Panboreal Superrealm lead us to conclude that there
are no major faunal gaps in Volgian successions of the Russian Platform and Northern Siberia. 相似文献
103.
Mikhail K. Kaban Alexey G. Petrunin Harro Schmeling Meysam Shahraki 《Surveys in Geophysics》2014,35(6):1361-1373
A joint effect of weak zones, dividing lithospheric plates, and lateral viscosity variations (LVV) in the whole mantle on the observed geoid is investigated by a new numerical approach. This technique is based on the substantially revised method introduced by Zhang and Christensen (Geophys J Int 114:531–547, 1993) for solving the Navier–Stokes–Poisson equations in the spectral domain with strong LVV. Weak plate boundaries (WPB) are introduced based on an integrated global model of plate boundary deformations GSRM (Kreemer et al. in Geophys J Int 154:8–34, 2003). The effect of WPB on the geoid is significant and reaches ?40 to 70 m with RMS ~20 m. The peaks are observed over large subduction zones in South America and the southwestern Pacific in agreement with previous studies. The positive geoid anomaly in South America could be explained largely by a dynamic effect of decoupling of the Nazca and South American plates. The negative changes of the geoid mostly relate to mid-oceanic ridges. The amplitude of the effect depends on the viscosity contrasts at WPB compared with the plate viscosity until its value reaches the limit of 2.5–3 orders of magnitude. This value might be considered as a level at which the plates are effectively decoupled. The effect of WPB exceeds the effect of LVV in the whole mantle and generally does not correlate with it. However, inclusion of LVV reduces the geoid perturbations due to WPB by about 10 m. Therefore, it is important to consider all factors together. The geoid changes mainly result from changes of the dynamic topography, which are about ?300 to +500 m. The obtained results show that including WPB may significantly improve the reliability of instantaneous global dynamic models. 相似文献
104.
舍尔金井位于俄罗斯东西伯利亚萨哈共和国雅库茨克市中心,总深度为116.5 m,是多年冻土区第一口深度超过100 m的井。井的挖掘从筹划到完工(1837年)历时10年,是俄罗斯商人费多尔·舍尔金(φедор Шергин)为挖井取水而建造的。舍尔金井的温度资料无可辩驳地证明了多年冻土的存在,它不仅是重要的文化和历史遗产,还是多年冻土存在的重要证据及冻土学发展的见证。 相似文献
105.
106.
A global isostatic gravity model of the Earth 总被引:3,自引:0,他引:3
Mikhail K. Kaban Peter Schwintzer & Sergey A. Tikhotsky 《Geophysical Journal International》1999,136(3):519-536
107.
Within the framework of the quasi-geostrophic approximation, the interactions of two identical initially circular vortex patches are studied using the contour dynamics/surgery method. The cases of barotropic vortices and of vortices in the upper layer of a two-layer fluid are considered. Diagrams showing the end states of vortex interactions and, in particular, the new regime of vortex triplet formation are constructed for a wide range of external parameters. This paper shows that, in the nonlinear evolution of two such (like-signed) vortices, the filaments and vorticity fragments surrounding the merged vortex often collapse into satellite vortices. Therefore, the conditions for the formation and the quasi-steady motions of a new type of triplet-shaped vortex structure are obtained. 相似文献
108.
Toby J. Boocock Sami Mikhail Julie Prytulak Tommaso Di Rocco Eva E. Stüeken 《Geostandards and Geoanalytical Research》2020,44(3):537-551
Thirteen commercially available silicate reference materials (RM) and one in‐house reference material, eleven of which have no previously published values, were analysed for nitrogen mass fraction and isotopic ratios with an Elemental Analyser (EA), and a Sealed Tube Combustion line, coupled to a continuous flow isotope ratio mass spectrometer (IRMS). These materials ranged from < 10 μg g?1 to 1% m/m nitrogen mass fractions and δ15N of ?0.5 to +19.8‰. Existing nitrogen RM BHVO‐2, MS#5 and SGR‐1b were used to assess the accuracy of the data from the sealed tube combustion line, which was found to be in good agreement with existing published values. In contrast, the EA‐IRMS failed to fully liberate nitrogen from all silicate rocks and minerals (achieving a mean of 44 ± 10% nitrogen yield) resulting in kinetic fractionation of isotope values by ?1.4‰ on average. Therefore, sealed tube combustion is better suited for analyses of silicate‐bound nitrogen. The EA worked reliably for organic samples, but care should be taken when using the EA for silicate nitrogen research. Moving forward, it is recommended that BHVO‐2, Biotite‐Fe, FK‐N and UB‐N be used as quality control materials as they appear to be most reproducible in terms of nitrogen mass fraction (relative error < 10%, 1s), and isotopic composition (< 0.6‰, 1s). 相似文献
109.
110.
J. S. Mikhail B. B. Baghos M. Y. Tawadrous Y. E. Helali H. Awad KH. I. Khalil M. El-Saftawe M. Ibrahim 《Earth, Moon, and Planets》1995,70(1-3):143-149
Clear air atmospheric transparency of eight nights at Helwan Observatory site during autumn period of 1987 have been determined using the yellow filter GG5. The prevailing atmospheric transmission extends to 58%. A comparison with previous values obtained with the same filter and site during autumn period of 1963 shows a considerable decrease at the present years in the clear air transmission of the site of Helwan. This can be attributed to the aerosol pollution of the site caused mainly by the increase of the industrial centers at Helwan Zone. Clear air atmospheric transparency values at the beginning of winter season and at spring season are also given. 相似文献