bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coherent annual and interannual variations in temperature and height fields in the tropical troposphere and lower stratosphere
Authors: Gage K. S. , Reid G. C. 
Published: February 2008

Radiosonde observations of temperature and height fields for 1953‐1969 have been analyzed for five tropical Pacific stations (Ponape, Guam, Yap, Eniwetok and Koror). These data have been combined to form monthly means averaged over all years and stations and annual means averaged over all stations.The analysis reveals a coherent annual variation consistent with the well‐known annual temperature wave in the tropics, i.e., a tropospheric cycle with warmest temperatures around April and May, and a roughly out‐of‐phase lower stratospheric cycle with coldest temperatures during the period December‐May. Comparing year‐to‐year variations in the tropospheric and lower stratospheric thermal fields, we find the out‐of‐phase relationship preserved. Periods of warm anomalies in the troposphere coincide with periods of cold anomalies in the stratosphere and vice versa. These observations are consistent with annual and inter‐annual variations in the intensity of the Hadley cell circulation.
Errors in the anisotropy of magnetic susceptibility and magnetic remanence of unconsolidated sediments produced by sampling methods
Authors: Gravenor C. P. , Symons D. T. A. , Coyle D. A. 
Published: February 2008

Samples from glacial varves were obtained by cutting cubes and by pushing plastic cubical containers into the sediment. The anisotropy of magnetic susceptibility results show that the mean angular difference in the kmax direction can be altered by 32° by pushing in the sample containers in a north to south versus an east to west direction. The values of lineation and Q are raised or lowered dependent upon the direction of push and the original fabric direction.Mean remanence directions can deviate by as much as 43° in a single clay layer dependent upon the direction in which the sample containers are inserted into the sediment. Corresponding changes in mean intensity of the remanence also demonstrate that the remanence has been affected by pushing in sample containers. The overall results underline the need to adopt trustworthy procedures for the sampling of soft sediments deposited by settling and traction.
On the existence of an extraterrestrial source of water vapor in the middle atmosphere
Authors: Reid George C. , Solomon Susan 
Published: February 2008

Observations of the ultraviolet dayglow of atomic oxygen from the DE‐1 spacecraft (Frank et al., 1986a,b) have revealed the existence of frequent localized decreases ("holes") in the emitted intensity. These have been interpreted as evidence of a steady influx of small "comets" whose icy envelope would provide a source of H2O molecules in the upper thermosphere. Using a one‐dimensional model of middle‐atmosphere composition, we show that the mesospheric water‐vapor concentration implied by this influx is much larger than the range of observed values.We suggest that the entry of such an icy object into the atmosphere at meteoric speeds is likely to lead to dissociation of H2O molecules, and to a primary downward flux of OH rather than H2O. This would reduce significantly the predicted increase in H2O concentrations in the mesosphere, and would introduce a different mechanism for the production of the airglow holes, i.e., chemical destruction of atomic oxygen by the fast reaction with OH.The constraints imposed on this scenario by the mesospheric water‐vapor measurements are examined, and we conclude that the permissible flux is some 30 times smaller than that proposed by Frank et al. The individual airglow holes would then have diameters of order 10 km instead of 50 km, and would be much less intense as seen by the DE‐1 instrument than those reported. We conclude that the mechanism, though relaxing the constraints on extraterrestrial water fluxes considerably, falls well short of explaining the observations.
A GCM simulation of the ozone seasonal variations at high latitudes in the Southern Hemisphere
Authors: Cariolle D. , Déqué M. , Morcrette J.‐J. 
Published: February 2008

A General Circulation Model is used to simulate the O3 seasonal variations in the Southern Hemisphere at high latitudes. The model reproduces many features of the stratospheric circulation and the ozone distribution.In particular a very cold and intense polar vortex develops from mid‐winter through spring and lasts until early November. The ozone content is minimum in the polar vortex, below 300 Dobsons, in spring. This value is still significantly higher than the amounts near 200 Dobsons recently measured in several Dobson stations in Antarctica. The possible deficiencies of the model photochemistry responsible for this discrepancy are discussed.The rapid polar ozone increase which follows the final warming is fairly well reproduced by the model. The warming starts in early November and is associated with an increase of the planetary wave 1 amplitude beyond 60° of latitude. The polar vortex follows a westward trajectory which starts from the pole and crosses over the Argentine Islands before vanishing at midlatitudes, in good agreement with observations.
P‐coda at distances 80° – 120° and structure beneath subduction zones: Example of Chile
Authors: Souriau Annie 
Published: February 2008

Strong phases are sometimes observed between P and PP for earthquakes at epicentral distances 80° – 120°. The present study analyzes as an example broadband data from a Chilean earthquake recorded in Europe by the NARS network, and by worldwide distributed GEOSCOPE stations. Clear phases are observed in the P‐coda only for the European stations.Underside reflections at upper mantle discontinuities beneath the PP bounce point at the Mid‐Atlantic Ridge are unable to explain these phases. A discontinuity in the lowermost mantle at the top of D″ is also discarded as a possible explanation.Reflections and conversions at a strong reflector about 200 km deep beneath Chile provide a satisfying explanation of the observations. The P‐coda is dominated by waves leaving the focus as S‐waves. The focal solution and the resulting radiation pattern explain the variations with azimuth and epicentral distance of the phases observed in the P‐coda.The reflector at 200 km beneath Chile may be the upper boundary of a piece of slab detached from the Nazca plate. Alternatively, it may result from the chemical differenciation of the slab during its subduction. Modelling P‐coda generated in other subduction zones may help to specify this differenciation process.
Distribution of the pCO2 in surface seawater of the western and central equatorial Pacific during the 1986/87 El Niño/Southern oscillation event
Authors: Inoue Hisayuki , Sugimura Yukio 
Published: February 2008

Measurements of the partial pressure of CO2 in surface seawater (pCO2) of the central and western equatorial Pacific were made in January and February 1987, with the main objective of studying variations in CO2 exchange between the air and the sea during the El Niño/Southern Oscillation (ENSO) event.In January 1987, the western equatorial Pacific had pCO2 distributions similar to those during non‐ENSO periods, despite the fact that large variations in pCO2 had occurred during the 1982/83 ENSO event.The pCO2 along 180° and 160°E was fairly constant (336.7 µatm to 355.7 µatm), while along 160°W it varied remarkably (342.8 µatm to 409.4 µatm). A maximum appeared near the equator, and the pCO2 was quite high from 3°N to 5°S (365.7 µatm to 409.4 µatm).In January and February 1987, the pCO2 in the surface seawater of the central equatorial Pacific was disturbed due to the ENSO event, but there seems to have been a net positive exchange of CO2 between the sea and air, compared to the 1982/83 ENSO event.
Analytical study of the relativistic dispersion: Application to the generation of the auroral kilometric radiation
Authors: Le Queau Dominique , Louarn Philippe 
Published: February 2008

The measurements recently performed by the Viking spacecraft have shown that, in addition to being cold plasma depleted, the source regions of the Auroral Kilometric Radiation (A.K.R.) are characterized by a relatively denser, more energetic electron component (a few perticle by cm−3, 〈E〉 ≈ 5 KeV). In order to properly study the Cyclotron Maser Instability (C.M.I.) which is thought to be responsible for the A.K.R. generation, it is thus necessary to include relativistic corrections in both the hermitian and the antihermitian parts of the dielectric tensor characterizing the linear properties of the plasma. Here one presents an analytical study of the corresponding dispersion equation which aims to describe stable and unstable waves having frequencies lying very close to the electronic gyrofrequency and propagating across the geomagnetic field with a perpendicular refractive index less than a few units (n⊥<5). The electronic population of the auroral plasma is supposed to have two components. The distribution function of the non‐thermal, energetic component is modelled by a Dory‐Guest‐Harris (DGH) distribution function and those of the tenuous thermal one by either a Dirac's function or a maxwellian. The dispersion equation thus depends on four parameters:i) the normalized peak energy of the DGH distribution: δ = 1/2 (v0/c)² which is a small number and scales both the temporal growth rate and the bandwidth of the CMI.ii) a parameter characterising the density of the energetic population: P = 1/δ(ωph/ωc)²(ωph being the plasma frequency of the energetic component).iii) the proportion of thermal plasma : χ = nc/nh where nc and nh are the density of the thermal and the hot plasma components respectively.iv) the ratio τ between the peak energy of the DGH and the mean energy of the maxwellian population.Our calculations allow us to simply perform a parametric study of the various regimes presented by the CMI. For the range of parameters inferred from measurements of the Swedish spacecraft Viking: (P>1 and χ small), the growth rate could maximize at the cut‐off frequency of the relativistic X mode. It can be quite large: Im(ω)max ≈ δωc (10−2 ωc for electrons of 5 Kev). Moreover, for small χ, the relativistic X mode is connected to freely propagating modes which guarantees an easy access of the electromagnetic energy to free space.
The redskin granite: Evidence for thermogravitational diffusion in a Precambrian granite batholith
Authors: Ludington Steve 
Published: February 2008

The 1000‐Ma‐old composite Pikes Peak batholith consists largely of medium‐ to coarse‐grained biotite granite but is intruded by several smaller granite plutons. Two of these, the Tarryall Mountains batholith and the Redskin Granite (Hawley, 1969; Hawley and Wobus, 1977), are here interpreted as cupolas atop the main mass of the Pikes Peak batholith.Chemical analysis for 38 elements in rocks from the Redskin Granite, the Tarryall Mountains batholith, and the biotite granite of the Pikes Peak batholith support the contention that the compositions of the smaller plutons are unlikely to have evolved from that of the main mass of the batholith by crystal fractionation. It is believed that these compositions arose through liquid‐state fractionation processes, possibly the convection‐aided thermogravitational model of Shaw et al. (1976).It is important to recognize that the chemical signature of this fractionation process can be discerned in holocrystalline rocks as well as in their glassy equivalents because the process may be instrumental in the formation of some kinds of lithophile ore deposits.
The use of Magsat data to determine secular variation
Authors: Cain Joseph C. , Frayser Jeffory , Muth Lorant , Schmitz Dave 
Published: February 2008

The appendix is available with the entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document B83‐004; $2.50. Payment must accompany order.A combined spatial and secular variation model of the geomagnetic field, labeled M061581, is derived from a selection of Magsat data. Secular variation (SV) data computed from linear fits to midnight hourly values from 19 magnetic observatories were also included in the analysis but were seen to have little effect on the model. The SV patterns from this new model are compared with those from the 1980 IGRF and with those for 1970 computed by the DGRF and with the 1960 patterns computed using the GSFC(12/66) model. Most of the features of the M061581 are identical in location and level with those of the 1980 IGRF. Together they confirm that the reversals in sign of field change seen over Asia and North America between 1965 and 1975 are reverting to the pre‐1965 states. The M061581 model gives −32 nT/yr for the dipole decay rate, larger than the 70% increase already reported since 1965. This abnormally high value is interpreted as being a defect of the model because it appears to result from a much larger (−100 nT/yr) drop in field over the polar regions not indicated by the 1980 IGRF. This north polar decrease is shown to be of external origin as the result of a combination of the seasonal effect of the north polar ionospheric (counterclockwise) afternoon Sqp cell increasing in intensity from the beginning (November 1979) to the end (June 1980) of the Magsat data collection period, coupled with an enhancement of its effect as the orbit lowered from the 350– 550 km initial altitudes to near 200 km just prior to burnup. This experiment indicates that secular variation can be obtained from satellite data for intervals of less than a full year if corrections can be made for seasonal effects and that ‘annual snapshots’ of the field by a satellite would allow easy and accurate models of secular change without the use of any surface data.
Focal mechanisms and depths of earthquakes in central Pakistan: A tectonic interpretation
Authors: Quittmeyer Richard C. , Kafka Alan L. , Armbruster John G. 
Published: February 2008

Focal mechanisms and depths for seven earthquakes in central Pakistan were determined from an analysis of Rayleigh waves of 20‐to 50‐s periods. In east‐central Pakistan, the nodal planes for some solutions strike obliquely to the grain of surface structures. This observation supports the contention of other workers that a thin surficial unit, decoupled from the basement along a surface of decollement, characterizes this region. In west‐central Pakistan, relative movement between the Indian and Eurasian plates is at least partially accommodated by seismic slip along the Chaman fault. Other faults, which are situated to the east of and lie subparallel to the Chaman fault, may also take up some of the relative plate motion. Observed activity within the zone of convergent‐type structure in central Pakistan may be a result of the greater component of convergence across the Indian‐Eurasian plate boundary north of Quetta, Pakistan.Appendix is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document B83‐010; $2.50. Payment must accompany order.
The residence time of the freshwater component in the Arctic Ocean
Authors: Östlund H. Göte 
Published: February 2008

The time function of bomb tritium concentrations in river runoff to the Arctic Ocean has been reconstructed from published data on tritium in precipitation 1959–1975. Tritium measurements on oceanic samples through the halocline exhibit strong linear relationships between tritium concentrations (TU values) and salinity. These waters thus look like binary mixtures of Atlantic source water and freshwater runoff. Combining these data, the vintage of the freshwater component in the Arctic Basin has been determined assuming no other major tritium source. The relation indicates the average age of the freshwater component to be 11±1 years in the Nansen Basin and the outflow and somewhat higher in the Canada Basin. According to tritium/salinity data, a surface layer of 10–60 m is affected by sea ice melting and freezing in the Nansen Basin, and the thickness of this layer increases to 150–170 m toward the Canada Basin. There is tritium also in the deeper waters, the unmixed Atlantic water, which points at residence times for that water not to exceed 17 years.The appendix is available with the entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document J81‐012; $1.00, payment must accompany order.
Equations of state and crystal structures of high‐pressure phases of shocked silicates and oxides
Authors: Ahrens Thomas J. , Anderson Don L. , Ringwood A. E. 
Published: February 2008

Shock‐wave data are now available for a variety of rocks, minerals, and oxides of geophysical interest in the pressure range appropriate for the lower mantle. These data are analyzed to obtain equation‐of‐state parameters with emphasis on the shock‐induced high‐pressure phases. Of twenty‐four materials for which Hugoniot data are analyzed, all but MgO, Al2O3, and MnO2 undergo at least one shock‐induced phase change below 800 kb. Birch‐Murnaghan parameters for the raw Hugoniots, metastable Hugoniots, adiabats, and 25°C isotherms are obtained for the high‐pressure phases. On correcting the raw Hugoniot data for MgO and Al2O3 for strength effects, we find that the calculated adiabatic equations of state are in good agreement with recent ultrasonic data. The zero‐pressure densities of high‐pressure phases are obtained by constraining the adiabats calculated from the Hugoniot data such that the zero‐pressure densities and the zero‐pressure slopes of the adiabats satisfy Anderson's seismic equation of state.Probable crystallographic structures of the high‐pressure phases are inferred from the classical laws of crystal chemistry and, in some cases, from static high‐pressure recovery experiments on analog compounds. Shock data for SiO2 (stishovite) indicate that transformation to the fluorite‐type structure (observed in TiO2) does not take place under shock, at least to ∼2000 kb. Fe2O3 probably transforms to either the perovskite or B rare earth structure with a zero‐pressure density of 5.96 g/cm³. MgAl2O4 (spinel) may transform to the CaFe2O4 structure with a zero‐pressure density of 4.19 g/cm³. Feldspars transform to the hollandite structure (density, of ∼3.85 g/cm³). Olivine‐rich rocks containing greater than 10% FeO either disproportionate to the ilmenite and rock salt structure or transform to a new post‐spinel polymorph having the Sr2PbO4 structure. Pyroxenes containing greater than 10% FeO probably transform to the ilmenite structure. High‐pressure forms of sillimanite and andalusite have calculated densities of 4.00 and 3.95 g/cm³, respectively. This probably represents disproportionation reaction products, Al2O3 + SiO2 (stishovite), which would give a density of 4.09 g/cm³. The Birch‐Murnaghan second‐order parameter ξ is nearly zero for MgO and Al2O3. 0.73 for stishovite, and ∼1 for the high‐pressure phases of the olivines and pyroxenes. The values of K′ = dK/dP are calculated along the Hugoniots and adiabats and are found to decrease at a rate of −0.5 to −1.6 cm³/g when the density is increased either by compression or by iron substitution.
Developments in seismic source theory
Authors: Archambeau Charles 
Published: February 2008

The basic stimulus for the development of a quantitative theory of seismic or earthquake sources is simply the desire to achieve some depth of understanding of this complex phenomenon. Beyond this intrinsic desire to unify and understand, a variety of applications of that understanding can be made which have considerable practical importance.In particular, the most important current applications of seismic source theory are to earthquake‐explosion discrimination and to earthquake prediction and control. Indeed, perhaps the greatest stimulus to theoretical work in seismic source theory in recent years has come from the diverse, and sometimes contradictory, observational data obtained in studies related to these particular problems. Thus while a large number of empirical relationships have been defined from the data, it is clear that a general theoretical framework is needed to unify the empirical results and to provide predictions outside the range and resolution of current observations as well as to provide deeper understanding of the meaning of the observations.
Paleomagnetism related to continental drift and plate tectonics
Authors: Van der Voo Rob 
Published: February 2008

This brief review article deals with those aspects of paleomagnetism that are related to continental drift, plate tectonics, and polar wandering. It is a sequel to a previous review paper (Van der Voo, 1975) and will not repeat the bibliography of that paper dealing with the U.S. contributions prior to 1974.The accomplishments and highlights of the past four years are reviewed below. This review will be followed by a rather personal assessment of the important open questions that are likely to be attacked in the next four‐year period. The bibliography contains a comprehensive listing of U.S. contributions in this field for 1974–1978, as well as selected publications from abroad. For a general treatment of paleomagnetism and plate tectonics the reader is referred to McElhinny (1973); recent listings of new paleomagnetic pole positions complement the data base of 1973 (McElhinny and Cowley, 1977, 1978; see also Hicken et al., 1972; Irving and Hastie, 1975; Irving et al., 1976a,b,c).
Physical properties of minerals and melts
Authors: Shankland T. J. 
Published: February 2008

This review summarizes measurements and theoretical developments for those physical properties of primary interest in geophysical calculations. It includes thermal properties, electrical conductivity, diffusion in minerals and melts, with only slight mention of the corresponding properties of rocks. Elastic properties and acoustic velocities are discussed; however, related work on equations of state and on plastic deformation are covered by Bell and Tullis in other reviews in this series. Knowledge of physical properties provides the basis for interpreting geophysical measurements of seismic velocities, electrical conductivity, and temperature gradients in terms of unknown quantities, such as mineralogical and chemical composition, temperature, heat flow, and fluid contents at depth in the earth and moon.The growth of this field as a specialty is signalled by several indications, for instance: books; Physics and Chemistry of Minerals and Rocks (Strens, 1976), High Pressure Research, Applications in Geophysics (Manghnani and Akimoto, 1977), each of which reports conference results; a new journal; Physics and Chemistry of Minerals; and topical meetings; the Mineral Physics Conference, Airlie, Virginia, October 1977.
Beobachtungen über die Eigenelectricität der atmosphärischen Niederschläge
Authors: Elster Von J. , Geitel H. 
Published: February 2008

Die electrischen Vorgänge in der Atmosphäre lassen sich zweckmässig unter drei Gruppen verteilen, deren erste diejenigen in sich schliesst, die auf der Existenz eines periodisch veränderlichen und im allgemeinen auch von Ort zu Ort verschiedenen electrischen Feldes in dem von eigentlichen Niederschlägen freien Luftraume beruhen, deren zweite die Störungen umfasst, die sich zugleich mit dem Auftreten von Niederschlägen innerhalb jenes Feldes einzustellen pflegen, während die dritte die Polarlichter und die mit ihnen verbundenen electrischen Wirkungen in sich begreift.Es ist möglich, dass die in diesen Gruppen zusammengefassten Vorgänge, obgleich sie alle das electrische Feld an der Erdoberfläche beeinflussen können, im wesentlichen von einander unabhängig sind und innerlich nicht enger zusammenhängen als etwa um ein Beispiel aus dem thermischen Verhalten der Atmosphäre zu wählen, die durch Insolation des Erdbodens herbeigeführte Temperaturerhöhung der Luft mit der in absteigenden Strömungen auftretenden Erwärmung, wie sie in dem Föhnphänomen beobachtet wird.