The stratospheric version of LMDz: dynamical climatologies, arctic oscillation, and impact on the surface climate     

François Lott  Laurent Fairhead  Frederic Hourdin  Phu Levan 《Climate Dynamics》2005,25(7-8):851-868

A climatology of the stratosphere is determined from a 20-year integration with the stratospheric version of the Atmospheric General Circulation Model LMDz. The model has an upper boundary at near 65 km, uses a Doppler spread non-orographic gravity waves drag parameterization and a subgrid-scale orography parameterization. It also has a Rayleigh damping layer for resolved waves only (not the zonal mean flow) over the top 5 km. This paper describes the basic features of the model and some aspects of its radiative-dynamical climatology. Standard first order diagnostics are presented but some emphasis is given to the model’s ability to reproduce the low frequency variability of the stratosphere in the winter northern hemisphere. In this model, the stratospheric variability is dominated at each altitudes by patterns which have some similarities with the arctic oscillation (AO). For those patterns, the signal sometimes descends from the stratosphere to the troposphere. In an experiment where the parameterized orographic gravity waves that reach the stratosphere are exaggerated, the model stratosphere in the NH presents much less variability. Although the stratospheric variability is still dominated by patterns that resemble to the AO, the downward influence of the stratosphere along these patterns is near entirely lost. In the same time, the persistence of the surface AO decreases, which is consistent with the picture that this persistence is linked to the descent of the AO signal from the stratosphere to the troposphere. A comparison between the stratospheric version of the model, and its routinely used tropospheric version is also done. It shows that the introduction of the stratosphere in a model that already has a realistic AO persistence can lead to overestimate the actual influence of the stratospheric dynamics onto the surface AO. Although this result is certainly model dependent, it suggests that the introduction of the stratosphere in a GCM also call for a new adjustment of the model parameters that affect the tropospheric variability.  相似文献   

North Atlantic Oscillation sensitivity to the El Niño/Southern Oscillation polarity in a large-ensemble simulation     

P. Melo-Gonçalves  A. C. Rocha  J. M. Castanheira  J. A. Ferreira 《Climate Dynamics》2005,24(6):599-606

A large ensemble modeling experiment with the Melbourne University General Circulation Model is presented. Thirty 17-year-long independent simulations were performed. All integrations were forced by the same observed sea surface temperatures, obtained from the Atmospheric Model Intercomparison Project II. The simulations were analyzed to assess the sensitivity of the North Atlantic Oscillation (NAO) to the El Niño/Southern Oscillation (ENSO) polarity. The results show signals of the ENSO phases both in the mean strength of the NAO as well as in its internal variability. During the cold ENSO phase, the probability density function of the NAO index presents a small but positive mean value, whereas it is negative during the warm ENSO phase. Also, the NAO variability associated with each ENSO phase shows a different behavior: during the warm phase the probability density function of the NAO index presents a larger variance and suggests a bimodality, whereas no bimodality is suggested in the cold phase.  相似文献   

Iodine concentrations of soils near Trabzon, Turkey: a region of endemic goiter     

E. ?ift?i  E. ?evketbeyo?lu  S. Tokel 《Environmental Geology》2007,53(2):457-465

Iodine contents of soils developed over the major rock formations of the northern zone of the Eastern Pontide Tectonic Belt (Northeastern Turkey) have been investigated with respect to soil-parent rock relationship, effect of topography, elevation, and climate to construe its effect on the health of the local population. Samples were collected from the A and B horizons of the soils developed over the major stratigraphic units constituting the eastern Pontides, including the Lower Basic Complex of Jurassic-Lower Cretaceous age, the Berdiga limestone (Jurassic-lower Cretaceous), the Dagbasi granitoid (Upper Cretaceous), volcano-sedimentary sequence of Upper Cretaceous age, ore-bearing and barren dacites of Upper Cretaceous age, and Neogene alkaline basalts. Chemical analyses of soil samples indicate significantly lower iodine abundances for all the soils studied (5–28 ppm) in comparison to the average abundance of iodine in analogous soils of other parts of the world (22–93 ppm). The concentration of iodine in soils developed over the same geologic formation decrease with increasing elevation. In certain cases, this decrease may reach up to 70%. Goiter is highly common throughout this region in Turkey. The results of this study suggest that the iodine deficiency of region’s soils may be a principal underlying cause for this area of Turkey being an endemic goiter region.  相似文献   

Molecular dynamics calculation of liquid iron properties and adiabatic temperature gradient in the Earth's outer core     

L. Ko&#;i  A. B. Belonoshko  R. Ahuja 《Geophysical Journal International》2007,168(2):890-894

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High-Frequency Hydroacoustic Monitoring in an Underground Iron Mine     

Séverine Bernardie  Jean-Pascal Gilbert  François Lebert  Hubert Fabriol 《Pure and Applied Geophysics》2007,164(1):177-197

The monitoring of the stability of old mines constitutes an important research objective for our institution, BRGM. The study reported here shows the contribution of high-frequency (>30 kHz) acoustic emissions to the detection of the damage within a rock mass, during an experiment within a pilot site of an old flooded iron mine. The experiment consisted of recording all the hydroacoustic events in a broad frequency band (between 30 Hz and 180 kHz), during 18 months. The monitoring network has been calibrated by a triggered block fall that made it possible to highlight a relationship between the occurrence of high-frequency/low-frequency hydroacoustic emissions and rock falls. The events recorded have been associated with the micro-failure of the rock mass near the roof, prior to the detachment of the blocks. This monitoring showed important high-frequency hydroacoustic activity, which may be associated with mechanical instabilities generated by the evolution of water pressure during the experiment. In conclusion, the high-frequency hydroacoustic activity appears to be a good indicator of instability and, therefore, this new technique constitutes a promising tool for monitoring abandoned underground cavities.  相似文献   

小口径散射伽玛能谱测井仪     

马延荣  刘振祥等 《中国煤田地质》2002,14(2):74-77

介绍散射伽玛能谱测井仪的组成工作原理、探测系统、探测技术、数据采集、处理及传输技术,能谱探测电路、数据采集电路及编制实时数据采集程序。并针对散射伽玛能谱测井在解决复杂岩性地层地质问题,确定空隙度、解释煤层气、裂隙带等方面的独具特点以及在煤田地质勘探中开展散射伽能谱测井的必要性进行了讨论。  相似文献   

Improvement of calcareous expansive soils in semi-arid environments   总被引：5，自引：0，他引：5  

Zalihe Nalbantoglu  Emin Gucbilmez 《Journal of Arid Environments》2001,47(4):453

The semi-arid climate and geology of Cyprus have caused the formation of calcareous expansive soils on the island. In some areas, swelling has caused serious foundation problems. The industrial by-product Soma fly ash has been used to improve the engineering properties of the soil. Fly ash treatment has shown tremendous potential as an economical method for the stabilization of the soil. Significant reduction in the swell potential and an increase in the hydraulic conductivity values are obtained. Use of fly ash with a small percentage of lime produces even more dramatic results. Cation exchange capacity (CEC) values substantiate the formation of the new pozzolanic reaction minerals which result in more stable silt-sand like structures.  相似文献   

Detecting small-scale targets by the 2D inversion of two-sided three-electrode data: application to an archaeological survey   总被引：2，自引：0，他引：2  

M. Emin Candansayar  Ahmet T. Ba&#;okur 《Geophysical Prospecting》2001,49(1):13-25

The detecting capabilities of some electrical arrays for the estimation of position, size and depth of small-scale targets were examined in view of the results obtained from 2D inversions of apparent-resistivity data. The two-sided three-electrode apparent-resistivity data are obtained by the application of left- and right-hand pole–dipole arrays that also permit the computation of four-electrode and dipole–dipole apparent-resistivity values without actually measuring them. Synthetic apparent-resistivity data sets of the dipole–dipole, four-electrode and two-sided three-electrode arrays are calculated for models that simulate buried tombs. The results of two-dimensional inversions are compared with regard to the resolution in detecting the exact location, size and depth of the target, showing some advantage for the two-sided three-electrode array. A field application was carried out in the archaeological site known as Alaca Hoyuk, a religious temple area of the Hittite period. The two-dimensional inversion of the two-sided three-electrode apparent-resistivity data has led to locating a part of the city wall and a buried small room. The validity of the interpretation has been checked against the results of subsequent archaeological excavations.  相似文献   

The chemical compositions and surface structures of two roAp stars with lithium spots (HD 83368 and HD 60435)     

A. V. Shavrina  N. S. Polosukhina  J. Zverko  V. Khalak  V. V. Tsymbal  J. Žižňovský 《Astronomy Reports》2001,45(10):784-796

The spectra of two roAp stars have been analyzed as part of a project to study lithium in magnetic Ap stars. Variability of the Li I 6708 Å resonance doublet and rare-earth lines was detected, which can be explained using an oblique rotator model with the lithium spots located at the magnetic poles. Synthetic spectra obtained at different rotational phases have yielded the first data on the atmospheric chemical compositions of these spotted stars. Using refined atomic data and the most complete line lists has enabled a detailed study of the spectra near the Li I 6708 Å line and computation of the Li I line profile taking into account the spotted distribution of the lithium over the stellar surfaces. The positions of two lithium spots and lithium abundances for each of the spots have been determined.  相似文献   

Ophiolite emplacement by strike-slip tectonics between the Pontide Zone and the Sakarya Zone in northwestern Anatolia, Turkey     

Ali Elmas  Erdinç Yiğitbaş 《International Journal of Earth Sciences》2001,90(2):257-269

Northwestern Anatolia contains three main tectonic units: (a) the Pontide Zone in the north which consists mainly of the Gstanbul-Zonguldak Unit in the west and the BallLda<-Küre Unit in the east; (b) the Sakarya Zone (or Continent) in the south, which is juxtaposed against the Pontide Zone due to the closure of Paleo-Tethys prior to Late Jurassic time; and (c) the Armutlu-OvacLk Zone which appears to represent a tectonic mixture of both zones. These three major tectonic zones are presently bounded by the two branches of the North Anatolian Transform Fault. The two tectonic contacts follow older tectonic lineaments (the Western Pontide Fault) which formed during the development of the Armutlu-OvacLk Zone. Since the earliest Cretaceous, an overall extensional regime dominated the region. A transpressional tectonic regime of Coniacian/Santonian to Campanian age caused the welding of the Gstanbul-Zonguldak Unit to the Sakarya Zone by an oblique collision. In the Late Campanian, a transtensional tectonic regime developed, forming a new basin within the amalgamated tectonic mosaic. The different tectonic regimes in the region were caused by activity of the Western Pontide Fault. Most of the ophiolites within the Armutlu-OvacLk Zone belong to the Paleo-Tethyan and/or pre-Ordovician ophiolitic core of the Gstanbul-Zonguldak Unit. The Late Cretaceous ophiolites in the eastern parts of the Armutlu-OvacLk Zone were transported from Neo-Tethyan ophiolites farther east by left-lateral strike-slip faults along the Western Pontide Fault. There is insufficient evidence to indicate the presence of an ocean (Intra-Pontide Ocean) between the Gstanbul-Zonguldak Unit and the Sakarya Zone during Late Cretaceous time.  相似文献