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1.
Summary The maintenance of the axisymmetric component of the flow in the atmosphere is investigated by means of a steady-state, quasi-geostrophic formulation of the meteorological equations. It is shown that the meridional variations in the time-averaged axisymmetric variables can be expressed as the sum of three contributions, one being due to the eddy heat transport, another to the eddy momentum transport, and a third to the convective-radiative equilibrium temperature which enters the problem through the specification of a Newtonian form of diabatic heating. The contributions by the large scale eddies are evaluated through the use of observed values for the eddy heat and momentum transports.The contributions from each of the three forcing mechanisms to the temperature and zonal wind fields are invstigated individually and found to be of about equal importance. The sum of the three contributions are also presented for the temperature, the zonal wind, the stream function associated with the mean meridional circulation and the corresponding vertical motion. Although the results fail to reproduce the main observed features of the lower stratosphere, they are found to be in good agreement with observations in the middle latitude troposphere. At any pressure level, for example, the computed mean zonal wind has a jet-like profile and the axis of the jet is found to slope to the south with height, as observed in the atmosphere.Based in part on a thesis submitted by the first author as partial fulfillment of the requirements for the Ph.D. degree at the University of Michigan. — Publication No. 194 from the Department of Meteorology and Oceanography, The University of Michigan. 相似文献
2.
V. E. Pavlov T. Yu. Tolmacheva R. V. Veselovskiy A. V. Latyshev A. M. Fetisova I. V. Bigun 《Izvestiya Physics of the Solid Earth》2017,53(5):702-713
Until recently, the existing data prevented the geophysicists from accurately dating the Bysy-Yuryakh stratum, which outcrops in the middle reach of the Kotuy River, constraining the time of its formation to a wide interval from the end of the Late Cambrian to the beginning of the Silurian. The obtained paleomagnetic data unambiguously correlate the Bysy-Yuryakh stratum to the Nyaian regional stage and constrain its formation, at least a considerable part of it, by the Tremadocian. This result perfectly agrees with the data on the Bysy-Yuryakh conodonts studied in this work and yields a spectacular example of the successful application of paleomagnetic studies in solving important tasks of stratigraphy and, correspondingly, petroleum geology. Within the Bysy-Yuryakh stratum, we revealed a large normal-polarity interval corresponding to the long (>1 Ma) period when the geomagnetic reversals were absent. This result, in combination with the data for the Tremadocian and Middle–Upper Cambrian sequences of the other regions, indicates that (1) the rate of occurrence of the geomagnetic reversals on the eve of the Ordovician Moyero superchron of reversed polarity was at most one reversal per Ma; (2) the superchron does not switch on instantaneously but is preceded by a certain gradual change in the operation conditions of the dynamo mechanism which, inter alia, manifests itself by the reduction of the frequency of geomagnetic reversals with the approach of the superchron. This finding supports the views according to which a process preparing the establishment of the superchrons takes place at the core–mantle boundary. 相似文献
3.
A special high-resolution routine of the EISCAT radar has been used to investigate the structure and development of the poleward wall of a deep trough in electron density. The feature was tracked by the radar during a 7-hour period under very quiet geomagnetic conditions. The field-aligned nature of the structure enabled an estimate to be made of the inclination of the geomagnetic field above EISCAT that was in good agreement with the current model. Observations of narrow field-aligned enhancements in electron temperature demonstrated that the wall of this trough is a dynamic feature, reforming regularly as the electron density responds on a time scale of tens of minutes to energy input from soft-particle precipitation. 相似文献
4.
M. S. Molodenskii S. M. Molodenskii D. S. Molodenskii T. A. Begitova 《Izvestiya Physics of the Solid Earth》2017,53(3):454-457
In (Molodenskii M.S. et al., 2016), the data from horizontal pendulums recording the tilts in the closest vicinity of the Great Tohoku earthquake of March 11, 2011 in Japan were analyzed. A significantly improved method for statistical analysis of the observational data enabled the authors to reveal a slow growth in tidal tilts during a period of six years before the earthquake, which was superseded by an instantaneous drop in the amplitudes at the time of the earthquake. After this, during the subsequent four years, the tidal amplitudes have remained at a significantly lower level than their average values before the earthquake. These changes in tidal amplitudes testify to the nonlinear character of the tidal response of the medium in the presence of large tectonic stresses: as is well known, the linear relationship between stresses and strains in a real medium is only the case for stresses that are far below the yield stress. When the stresses approach the failure limit, two counteracting effects come into play: (1) the shear moduli in some areas decrease as a result of the avalanche growth of the crack formation processes, and (2) the moduli increase due to the compression in the other areas. Irrespective of which particular effect of these two is predominant, in either case the linearity of the relationship between the stresses and strains should be violated. This violation cannot but affect the amplitudes of the tidal tilts and strains characterizing this relationship in the presence of fairly low additional tidal stresses (i.e., the derivative of the off-diagonal stress tensor components with respect to the same components of the strain tensor). Since there is presently a sufficiently dense network of the horizontal pendulums recording the tilts (the global IRIS network and the particularly dense F-NET network in Japan), monitoring the changes in the amplitudes of tidal tilts can be considered as a key instrument for capturing the signs of the approach of tectonic stresses to their critical values. The increase in tidal amplitudes before the Tohoku earthquake and their drop at the moment of the earthquake, which were revealed by us, as well as the constancy of the amplitudes during four years after the event, unambiguously indicate that the accumulation of tectonic stresses caused the growth in tidal amplitudes, whereas the stress release by the earthquake caused their diminution. This does not however mean that stress accumulation is accompanied by a decrease in the elastic moduli and that the release of stresses is accompanied by the growth of elastic moduli all over the source area. As was shown in (Molodenskii M.S. et al., 2012), even in the simplest model of spatially homogeneous variations of elastic modules, the variations in tidal tilts are an odd function of the distance from the epicenter. Therefore, irrespective of whether the elastic moduli decrease or increase, the amplitudes of tidal tilts should decrease in some areas and increase in other areas. Hence, the very fact of the growth of tidal tilt amplitudes with time cannot be considered as a sign of the growth of tectonic stresses. To be positive about the latter, one should make sure that the consistent (unidirectional) changes have been observed during a sufficiently long time interval and that their magnitudes were significantly larger than the measurement errors. Hence, it is important to reliably estimate the errors of the observational data. 相似文献
5.
Prof. Dr. W. A. Heiskanen 《Pure and Applied Geophysics》1958,41(1):1-18
Summary The author mentions the aims of the World-wide gravity project he established in the Ohio State University in Columbus, in 1950. He outlines the practical procedure of the gravimetric computations of the undulationsN and the vertical deflection components and and emphasizes that only by the global international cooperation and additional gravity observations at sea carried out during the last decade it has been possible to gather to Columbus the needed gravity material. Since there exist still large gravimetrically unsurveyed areas it is of vital significance to study what gravity anomalies are best to be used for these regions. The given figures concerning the accuracy of theN, and , estimated theoretically and obtained in practice, indicate that in the gravimetrically well surveyed parts of the world like in Europe and the United States we can get gravimetrically on basis of existing gravity material theN-values with accuracy of about 5–10 meters, and and with the accuracy of about 1. The geoid undulationsN are already computed in Columbus for more than 6000 points of the northern hemisphere. The sample maps show the interesting geoid of Europe and vicinity between the latitudes 60° and 30° and longitude 5° W and 30° E, drafted on basis of more than 1000N-values computed at the corners of 1°×1° squares. It is interesting to realize that the geoid undulations in all this area are positive, the extreme values being between 40 and 50 meters. The geophysical significance of the geoid maps of this kind is pointed out. 相似文献
6.
7.
Geomagnetism and Aeronomy - The evolution of the magnetic configuration in the solar corona is studied. The curvature of the K-corona helmets obtained from an analytical approximation of the... 相似文献
8.
The idea of predicting earthquakes by continuously monitoring temporal variations in the tidal response of the medium was suggested by Beaumont and Berger in 1974. However, it became possible to implement the idea only recently. This possibility has arisen due to the deployment of Global Seismic Network (GSN), which collects the data on tidal tilts and gravity in the epicenters of strong earthquakes before and after the strongest events. In this paper, we present the results of model analytical and numerical calculations of the elastic displacements of the Earth’s surface caused by the earthquakes and their preparatory processes. The analytical calculations are limited to the model of a uniform elastic halfspace; the numerical calculations, in addition to this model, also cover the models with radially heterogeneous distributions of elastic moduli in the crust and in the upper mantle, which are determined by the PREM model. We describe the results of modeling temporal variations in the tidal response of the medium in the vicinity of the source of a catastrophic earthquake. The model of seismic source is specified by the length and the orientations of the fault plane and by the value of the discontinuity in the tangential component of the displacement vector on the opposite sides of the fault. The model is based on the GPS data on the horizontal and vertical displacements of the Earth’s surface. We suggest the method for determining temporal changes in the tidal response of the medium in the seismically active regions. This method improves the sensitivity and time resolution of the standard techniques of sliding-window analysis by more than an order of magnitude. The comparative analysis of temporal variations in the tidal response of the medium in the zones of the magnitude 9 earthquake in Japan (March 9, 2011) illustrates the described approach.
相似文献9.
The idea of predicting earthquakes by continuously monitoring temporal variations in the tidal response of the medium was suggested by Beaumont and Berger in 1974. However, it became possible to implement the idea only recently. This possibility has arisen due to the deployment of Global Seismic Network (GSN), which collects the data on tidal tilts and gravity in the epicenters of strong earthquakes before and after the strongest events. In this paper, we present the results of model analytical and numerical calculations of the elastic displacements of the Earth??s surface caused by the earthquakes and their preparatory processes. The analytical calculations are limited to the model of a uniform elastic halfspace; the numerical calculations, in addition to this model, also cover the models with radially heterogeneous distributions of elastic moduli in the crust and in the upper mantle, which are determined by the PREM model. We describe the results of modeling temporal variations in the tidal response of the medium in the vicinity of the source of a catastrophic earthquake. The model of seismic source is specified by the length and the orientations of the fault plane and by the value of the discontinuity in the tangential component of the displacement vector on the opposite sides of the fault. The model is based on the GPS data on the horizontal and vertical displacements of the Earth??s surface. We suggest the method for determining temporal changes in the tidal response of the medium in the seismically active regions. This method improves the sensitivity and time resolution of the standard techniques of sliding-window analysis by more than an order of magnitude. The comparative analysis of temporal variations in the tidal response of the medium in the zones of the magnitude 9 earthquake in Japan (March 9, 2011) illustrates the described approach. 相似文献
10.
D. Zidarov 《Pure and Applied Geophysics》1973,105(1):655-668
Summary The paleomagnetic field (declination and inclination) in different geological epochs is represented through the field of the so-called magnetic dipole. The optimal dipole coordinates so obtained show that during older geological times the optimal dipole lay outside the earth's centre and moved towards and around the earth centre. It is supposed that the optimal dipole trajectory in the earth coincides with earth core trajectory. This core motion brought about a motion of the masses of the mantle in a direction opposite to the motion of the core. This in turn brought about the break-down of Pangea and the separation of the continents. The drift of the continents, the relative changing of the earth's rotational axis and many other geological and geophysical phenomena may be explained through such a motion, that is through the motion of an eccentrical core towards the earth centre. 相似文献
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12.
The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth. 相似文献
13.
Summary The boundary problem of the potential theory is treated for the case in which the values of the vertical derivative of the gravity anomaly are known. There boundary conditions are derived and alternatives are also treated.Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday 相似文献
14.
Kapralova V. N. Chesnokova I. V. Makarycheva E. M. Sergeev D. O. 《Water Resources》2019,46(2):S81-S86
Water Resources - The dynamics of the talik zones, associated both with the internal cyclical nature of their development and with climate changes, leads to temporary differences in the volume of... 相似文献
15.
As is known, the secular deceleration of the Earth's diurnal rotation is explained mainly by the tidal friction in the ocean. Below we consider this mechanism in some detail, taking into account also elastic deformations of the mantle under the action of ocean loading and the interaction between the tide-generating body, ocean tidal wave, liquid outer core, and solid inner core. It is shown that elastic displacements of the core-mantle boundary under the action of ocean loading are of about the same amplitude and phase as the elastic loading displacements of the Earth's outer surface. As a result, side by side with the mechanism of secular deceleration of diurnal rotation of the mantle, there are also (1) the opposite mechanism of secular acceleration of diurnal rotation of the outer liquid core and of the solid inner core and (2) the mechanism of excitation of differential rotation in the liquid core. Taking these effects into account, we compare theoretical and modern observed data on the eastward drift of the solid inner core. It is shown that the best agreement may be obtained if the turbulent viscosity of the liquid core is about 2 × 10
3
Poise 相似文献
16.
应用伪谱法研究了地壳各向异性对上地幔各向异性分析的影响. 用几种不同情况下的两层各向异性模型,模拟了全波场,着重分析了不同深度观测点上的剪切波分裂特征. 结果表明,当地壳为各向同性或其各向异性主轴与上地幔重合或相互垂直时,在地壳观测到的快、慢剪切波的偏振方向保持了上地幔中的偏振方向;重合时,快、慢波走时延迟增大;垂直时,走时延迟减小. 当地壳的各向异性主轴与上地幔成一般夹角时,其粒子运动轨迹变得十分复杂,不能直观地识别上地幔各向异性中的快波方向,对走时延迟也有一定的影响. 将常用的两种分析方法应用于对模拟结果的反演,发现当地壳各向异性与上地幔各向异性方向为一般夹角时,反演结果会出现较大的误差或误判. 进而提出解决这一问题的方法,一是综合多种方法的结果;二是由拟合残差或相关系数等值线作进一步的确定. 相似文献
17.
The structure of the vector field of present-day horizontal velocities on the Earth’s surface is investigated with the use
of the territory covered by the Central-Asian GPS network as an example. A method of identification of groups of GPS points
(statistically rigid clusters), for which the rate of change in distances between them is virtually zero, is proposed and
realized. Sites of the Earth’s surface (regions) containing such groups of GPS points, within the required measurement accuracy,
move in the horizontal plane as two-dimensional rigid bodies. The clustering algorithm, which is based on the Student t statistics in determining the so-called statistical “sample cost,” is developed and carefully tested. The results of identification
of regions take into account possible random errors in velocity measurements and do not depend on the chosen frame of reference.
The method of identification of regions is sufficiently stable with respect to variations in the number of GPS sites used
for clustering. Of all the sites of the Central-Asian GPS network, 323 points were selected for clustering. These sites were
measured from 3 to 11 times over an 11-year interval of observations (1995–2005). The estimates of errors of velocity measurement
for these sites must not exceed 1.0 mm/yr. As a result, 29 statistically rigid clusters, containing from 3 to 17 GPS sites,
were identified, and the kinematic regimes of motion of regions corresponding to these clusters were determined with respect
to the stable part of Eurasia. With the general direction of the translatory motion of regions toward the north, the majority
of them rotate counterclockwise. Nearly one third of GPS sites do not participate in the formation of clusters; these points
fall into the interregional space (IRS), which is characterized by increased strain rates. The IRS structure is partitioned
into zones with four directions, of which two directions virtually coincide with directions of the principal axes of the regional
strain rate tensor, and the two other directions are oriented diagonally to the principal axes. The axis of the maximum rate
of the regional shortening has a north-northwestern orientation. It is in this direction (mainly along the IRS) that the crust’s
contraction takes place. There is no spatial correlation between IRS zones and geological faults; however, their angular distributions
and the directions of strike-slips on them are interrelated. The resulting patterns of regional motions and IRS deformations
consistently reflect the dynamic action of the Indian plate on the territory under investigation. 相似文献
18.
The geodynamic interpretation of the results of GPS observations among the permanently operating stations which establish the frame for defining and conserving the coordinate system and simultaneously for describing the fundamental tendencies of dynamics in the area represented by them, should be deprived of the effects of geodynamic phenomena, which can be either periodic or short-term (even non-periodic) so that secular changes may be found. Some of these influences are included in scientific processing software, others have to be modelled later. The purpose of this project is to determine the influences of the indirect effect of ocean tides and the direct deformational effect of the atmosphere on the results of GPS observations, performed at stations Pecný (Czech Republic), Wettzell (FRG) and Graz (Austria), and also for the GPS stations of the Central Europe Regional Geodynamic Project (CERGOP) in the region of Central and East Europe. On the basis of analyses and results it is possible to claim that at the present accuracy of GPS observations the influence of ocean loading and atmospheric pressure effects for geodynamic campaigns in the region of the Czech Republic is negligible. For campaigns in larger regions (i.e. Central Europe) atmospheric corrections will have to be applied to height differences. These corrections, however, due to their periodicity have negligible influence on secular changes. 相似文献
19.
The biology and purity of the water in three profiles of the Oder River in its upper stream on the Czechoslovak territory were investigated in the course of 1979… 1980. Zoobenthos, physical and chemical parametres, and microbiological germs were analysed. The bioseston was considered only briefly. On the basis of the presented material the Oder enters the Ostrava industrial agglomeration as a betamesosaprobic stream (Class I b of water purity), in spite of the fact that many sources of pollution can be found in this section of the river. Physical and chemical parameters can be assessed in a similar way. The Oder River belongs to Class III of water purity according to microbiological ratings. 相似文献