bluuebunny/crossref_metadata_2025_split huggingface dataset:
Buoyancy waves in the troposphere: Doppler radar observations and a theoretical model
Authors: VanZandt T. E. , Green J. L. , Clark W. L. , Grant J. R. 
Published: February 2008

On 15‐16 April 1976 a polar‐front jet stream with northward winds as large as 70 m/s passed over Colorado. Profiles of the radial component of the velocity vr and refractivity turbulence structure constant Cn² were observed by the Sunset VHF pulsed Doppler radar, near Boulder, CO, from near the ground up to about 15km, with 67s time resolution and lkm height resolution. While the jet stream was overhead, vr and Cn² fluctuated continuously with time scales from a few minutes up to hours. On several occasions coherent wave trains with periods ranging from 4 to 8 minutes were observed. The corresponding pressure perturbations at the ground were measured by a nearby microbarograph array. One of these events is discussed here.These observations are compared with the results of a linear stability analysis of the background wind and temperature profiles. The theoretical predictions of the period, wavelength, and phase speed, and the corresponding height variations of the phase and amplitude of the perturbation velocity along the radar beam all agree well with the observations. This agreement demonstrates that (1) the short‐period waves were generated by shear instability on the bottom of the jet stream and (2) linear theory can adequately describe many features of buoyancy waves generated by dynamic instability.
Evidence for sea breezes on the Alaskan Beaufort Sea Coast
Authors: Kozo Thomas L. 
Published: February 2008

Atmospheric environmental data collected in August 1976 and 1977 along the Beaufort Sea coast of Alaska exhibited both circumstantial and direct evidence of the existence of sea breezes at 70°N latitude. To estimate the total atmospheric boundary layer turninga two‐dimensional least squares technique was used to derive the three hourly gradient wind (above the atmospheric boundary layer) with data from surface pressure stations for simultaneous comparison to surface wind data. Results indicated the average turning of the wind from above the boundary layer to the surface was 120° on sea breeze days. Rotary spectra from time series data of surface winds measured at offshore and onshore sites have shown the horizontal extent of the sea breeze influence to include at least a 37 km zone centered on the coastline.The sea breeze is largely responsible for the increased persistence of surface onshore (northeasterly and easterly) winds documented in August historical data for the Alaskan Beaufort Sea coast.
Temperature dependence of the rate coefficient for charge exchange of metastable O+(²D) with N2
Authors: Torr M. R. , Torr D. G. 
Published: February 2008

Using a database of aeronomical parameters measured by the Atmosphere Explorer‐C satellite, we deduce a temperature dependence of the reaction rate coefficient for the charge exchange of O+(²D) with N2, The results indicate that the Atmosphere Explorer values determined over the temperature range ∼700 to 1900°K, are not in conflict with the laboratory measurements made at higher temperatures. From these results, we show that the rate coefficient can be represented by and The shape of the temperature variation is found to be similar to that for the ion atom interchange rate coefficient of ground state oxygen ions with N2.
Large scale 6300Å, 5577Å, 3914Å dayside auroral morphology
Authors: Murphree J. S. , Cogger L. L. , Anger C. D. , Ismail S. , Shepherd G. G. 
Published: February 2008

Simultaneous observations at 6300Å, 5577Å, and 3914Å by the ISIS‐2 satellite are used to examine the morphology of auroras in the noon sector. While a minimum in intensity is generally observed in the 5577Å and 3914Å emissions from approximately 10 to 12 MLT, the 6300Å emissions may be most intense there. The latitudinal extent of 6300Å emissions is much greater than that of 5577Å and 3914Å and discrete features are generally not apparent in the 6300Å emission. Peak levels of 6300Å emission may occur at noon, prenoon, or afternoon and thus 6300Å emission is not confined to the "gap" or minimum in the day side discrete aurora seen at 5577Å and 3914Å. Substantial 6300Å emission occurs on closed field lines which is evidently due to boundary layer plasma. No optical signature of direct entry particles is identified.It is apparent that large differences in morphology and intensity exist between wavelengths in dayside auroras due to different source regions for the precipitating particles. For example, Cogger et al. (1977) have pointed out that the gap in dayside emissions (observed at 5577Å) is really a wavelength dependent feature in that 6300Å measurements indicate a maximum at noon rather than a gap (Shepherd and Thirkettle, 1973; Shepherd et al., 1976). Whalen and Pike (1973) have also shown that an enhanced band of 6300Å emission occurs across the dayside and when discrete midday auroras occur they locate within this band. Heikkila et al. (1972) have used 4278Å and 6300Å data from aircraft flights and satellite particle measurements to characterize the nature of the particle precipitation and the resulting aurora on the dayside. However, with ground based or direct satellite observations only a single meridian can be observed in a short period of time.In this paper, the "instantaneous" relationship between 6300Å, 5577Å and 3914Å emissions in the entire noon sector is studied to provide new information of the two dimensional morphology of these emissions. The data were taken by the Auroral Scanning Photometer (ASP) and the Red Line Photometer (RLP) on ISIS‐2 during the northern hemisphere winter solstice period in December 1974.
Mountain barrier baroclinity effects on surface winds along the Alaskan Arctic Coast
Authors: Kozo Thomas L. 
Published: February 2008

The deployment of offshore pressure and position relaying buoys in February 1979 within the arctic ice pack has allowed for a more complete investigation of a wintertime mesoscale meteorological effect known as mountain barrier baroclinity (MBB). Total atmospheric boundary layer turning with height was estimated by comparing computed three hourly geostrophic winds (above the boundary layer) to simultaneous surface winds at Barter Island, Alaska. This total turning compared closely with wind velocity versus height data obtained through rawinsonde launches at Barter Island. Results indicate that the average turning of the wind from above the boundary layer to the surface was 140° during periods of MBB influence. In addition the average difference between simultaneously measured surface winds at Barter Island and Pt. Barrow, Alaska (during MBB periods) was 140°, which cannot be explained by existing synoptic (large‐scale) weather charts.The evidence explains the wintertime abundance of west to southwest winds seen on historical monthly wind direction histograms from Barter Island (64 km north of the Brooks Range) while Pt. Barrow (300 km north of the Brooks Range) histograms for similar months show an east to northeast bias. Finally, the occurrences of the MBB effect and a summertime sea breeze effect have been related to arctic tundra surface albedo.
The isotopic composition of argon included in an Arkansas diamond and its significance
Authors: Melton Charles E. , Giardini A. A. 
Published: February 2008

The isotopic composition of argon entrapped in a 6.3 carat, Type I, Arkansas, U. S. A. diamond (emplacement date 106 ± 3 m.y. ago) has been determined by mass spectrometric techniques. This was done by crushing the stone in a diamond crusher attached to the high vacuum inlet system of a high‐sensitivity research mass spectrometer. The results show an 40Ar/36Ar value of 189 compared to a ratio of 294 for atmospheric argon, and an 38Ar/36Ar value of 0.18 almost identical to that for atmospheric argon (0.19). The isotopic data have been applied to a model of the outer Earth to test the crystallization age of the diamond. The results may be interpreted in terms of diamond crystallization about 3.1 billion years ago.The existence of primordial 36Ar and 38Ar (non‐radiogenic isotopes) shows that the Earth had not completely degassed at the time of diamond crystallization. In fact, if the diamond is assumed to be a representative sample of the upper mantle with respect to fluid content, the mass of primordial 36Ar in this region of the Earth is calculated to be 1 × 1010 tons at the time of diamond crystallization, or 2.5 × 10−5 ppm by weight.
Coincident radar and rocket observations of equatorial spread‐F
Authors: Szuszczewicz E. P. , Tsunoda R. T. , Narcisi R. , Holmes J. C. 
Published: February 2008

Coordinated measurements of equatorial spread‐F conducted during July 1979 at the Kwajalein Atoll have yielded the first definitive space‐ and time coincident radar and rocket observations of small scale irregularities and large scale plasma depletions. The results have shown that:(a) During conditions of well‐developed equatorial spread‐F the most intense "in situ" irregularities occurred on the bottomside F‐layer gradient.(b) Within a large scale topside F‐layer depletion radar backscatter and "in situ" irregularity strengths maximized near the depletion’s upper wall.(c) Ion composition within a topside depletion provided signatures of its bottomside source domain and estimates of average maximum vertical drift velocity. For long‐lived depletions, it was found that molecular‐ion signatures (NO+ and O2+) can be lost while bottomside levels of N+ can be maintained when [O+] ≈ Ne ≫ [NO+] + [O2+]; and finally,(d) Large scale fluctuations of O+ accompanied by a near‐constant level of NO+ and O2+on the bottomside F‐layer gradient suggests that neutral atmospheric turbulence is not a major source for bottomside ionospheric plasma irregularities and the associated triggering of equatorial spread‐F.
Observations of double arch formation in the Bering Strait
Authors: Torgerson Lenora J. , Stringer William J. 
Published: February 2008

During the time that ice is present in the Bering Strait, it is constantly moving, both northward and southward, subject to wind and current stresses. There were, however, several times in the last decade when the ice was prevented from travelling through the Strait. The blockage of ice was due to the formation of fairly stable double arches that extended across the Strait.Six episodes of double arch formation, resulting in ice blockage in the Bering Strait, were recorded on NOAA satellite imagery spanning the last eleven years; one additional episode was seen on Landsat imagery. All of the incidences of double arching occurred between February and May. In the most extreme case the arches prevented the southward flow of ice through the Strait for at least 27 days during April and May 1980.
A model of comet P/Giacobini‐Zinner
Authors: Boice D. C. , Huebner W. F. , Keady J. J. , Schmidt H. U. , Wegmann R. 
Published: February 2008

A computer model of Comet P/Giacobini‐Zinner is presented which contains photo‐processes, gas‐phase chemical kinetics, energy balance, multifluid hydrodynamics with a transition to free molecular flow, and solar wind interaction. Recently, the physics for electrons in the model has been improved by including electron impact ionization and dissociation and separately accounting for electron energetics. Electron heating and cooling mechanisms include photoprocesses, recombination processes, inelastic and elastic collisions with heavy molecules, and expansion cooling. The model incorporates an internally consistent interaction of the solar wind with the coma gas using the axisymmetric ideal fluid dynamic equations.The nuclear size and composition have been chosen to make the calculations relevant to the 11 September 1985 International Cometary Explorer (ICE) encounter with Comet P/Giacobini‐Zinner. Model profiles of the temperature, velocity, and number density of the electrons are in good agreement with measurements along ICE's trajectory. These results indicate that the probe passed through a region of the coma at the onset of the plasma tail.
First analyses of broadband records on the Geoscope Network: Potential for detailed studies of mantle discontinuities
Authors: Souriau Annie 
Published: February 2008

Examples of the first analyses of broadband GEOSCOPE data at station SSB (France) show that these data will make possible a detailed study of the deep mantle discontinuities.Analysis of the P‐coda of earthquakes using specific methods suggests the existence of P to S conversions at 670 km depth beneath SSB for earthquakes with northern to eastern azimuths; a comparison with results from the NARS and Grafenberg arrays indicate that the 670 km discontinuity beneath western Europe is highly heterogeneous or horizontally discontinuous. A frequency analysis reveals that the relevant discontinuity is not very sharp ( ∽ 20 to 70 km thick). Besides, a sharp ( < 5 km thick) discontinuity at 900 km depth is observed beneath the Mid‐Atlantic Ridge from P reflections, giving PP precursors, for the strong March 1985 Chilean earthquake, but no 670 km discontinuity seems to be present beneath the Ridge.
Off‐line acquisition of crustal reflection and refraction data
Authors: Milkereit B. , Bittner R. , Meissner R. 
Published: February 2008

A piggy‐back seismic reflection survey was carried out in 1984 as part of the DEKORP 2‐S profile. The signal from explosive‐sources was digitally recorded on 120 channels. The objectives were: a) To record crustal reflections at a wide range of incidence angles (5‐85 km offset) b) To provide 3‐D control of deep crustal reflectors seen on the main profile.An important consideration throughout the fieldwork was to avoid interference with the main reflection survey. This experiment showed that explosive charges as small as 5‐90 kg may provide sufficient energy for observations from the steep‐angle to the wide‐angle range. The off‐line position of the receivers allowed the reconstruction of steep‐angle reflection profiles parallel and perpendicular to the main reflection line. A strong diffraction cluster on the main line could be correlated laterally, and indications about the diffractors' shape could be obtained.
Effects of near source bathymetry on teleseismic P waveforms
Authors: Wiens Douglas A. 
Published: February 2008

Teleseismic P waveforms from submarine earthquakes show water reverberations that are often poorly modeled by synthetic seismograms. This study suggests that considerable misfit results from the non‐horizontal nature of the seafloor in the epicentral region and examines this effect for a planar dipping water‐crust interface. Geometric ray theory synthetics calculated for a double‐couple source show that P waveforms are extremely sensitive to seafloor orientation. Because of the large impedance contrast across the boundary, seafloor dips as small as 0.5° significantly modify the ray paths, affecting the take‐off angle at the source, reflection and transmission coefficients at the interface, geometric spreading, and travel time.To test the applicability of such modeling, P waveforms from the March 29, 1976 Cocos Ridge intraplate earthquake were studied. The waveforms, many of which show prominent water multiples poorly modeled with flat lying bathymetry, were inverted for the best‐fitting planar ocean bottom orientation using a grid search technique. Synthetics computed for the best fitting seafloor orientation match the data much better than synthetics for a flat lying structure, and reproduce the observed azimuthal dependence of water multiple amplitudes. The derived ocean bottom dip angle and direction are in agreement with bathymetric charts, suggesting P waveforms provide constraints on the seafloor orientation in the epicentral region. Green's functions incorporating the effects of bathymetry should provide better resolution of the source parameters of submarine earthquakes.
Neutral surfaces in the ocean: Implications for modelling
Authors: McDougall Trevor J. 
Published: February 2008

Surfaces of neutral static stability (neutral surfaces) along which lateral ocean mixing occurs, can be quite different to potential density surfaces. For example, the lateral gradients of potential temperature may differ in the two surfaces by up to a factor of four in some extreme but important regions. Vertical mixing processes cause vertical upwelling velocities that can be modelled as vortex‐stretching terms in layered models of ocean circulation. However, since potential density surfaces are commonly inclined with respect to neutral surfaces, lateral motion along neutral surfaces also gives rise to unwanted vertical motion through isopycnals that is not related to vertical mixing processes.When considering the conservation of potential vorticity in the real ocean, the differences between the depths of neutral surfaces and potential density surfaces becomes quite important. Neutral surface potential vorticity (NSPV), is introduced, defined to be proportional to f/h, where f is the Coriolis parameter and h is the vertical distance between adjacent neutral surfaces. NSPV is often significantly different (by factors of 2 or 3) to the two other commonly used potential vorticity variables, isopycnal potential vorticity, IPV, and fN².
Two‐dimensional modelling of the Antarctic lower stratosphere
Authors: Chipperfield M. P. , Pyle J. A. 
Published: February 2008

We have used a two‐dimensional radiative‐dynamical‐chemical model to study some aspects of Antarctic ozone depletion. While many aspects of the preconditioning of the vortex are reproduced by simply reducing the horizontal diffusion during the Antarctic winter and early spring, significant problems remain. The lack of knowledge of the meridional circulation throughout the year represents a serious limitation.When a springtime ozone depletion is imposed on the model in the Antarctic, the effect of the depletion is confined mainly to high southern latitudes. The consequent changes in radiative transfer lead to lower temperatures in the lower polar atmosphere during spring, with some smaller increases in temperature above about 20mb.
Seasonal variation of some constituents of Antarctic tropospheric air
Authors: Hogan A. W. , Egan W. G. , Samson J. A. , Barnard S. C. , Riley D. M. , Murphey B. B. 
Published: February 2008

The interior of Antarctica is dominated by the continental Antarctic [cA] air mass, which resides entirely on the antarctic ice, and only receives heat, moisture and particles by exchange with surrounding air masses. The concentrations of carbon dioxide, total aerosol, and soot aerosol do not vary coincidentally in this air mass during antarctic spring.A hypothesis describing the modification of these properties within the cA air mass through exchange with the surrounding air masses and variation of the source strength of marine aerosol in maritime polar air masses is proposed.
Ionospheric convection and currents in the midnight sector on November 8, 1979
Authors: Foster J. C. , Doupnik J. R. , Stiles G. S. 
Published: February 2008

Chatanika Radar observations of ionospheric convection velocities spanning auroral latitudes (58°–75°Λ), and contours of electrostatic potential derived from them, are described for a period of moderately strong geomagnetic activity in the midnight sector. Digitized H component magnetograms and contours of magnetic perturbation, ΔH, derived from them are presented in order to compare the convection pattern and radar‐deduced currents with the observed ground response to the auroral electrojets. In spite of midnight sector substorm activity, the convection pattern maintains a two cell character. The latitude of greatest negative potential in the evening sector, determined from the radar data, accurately denotes the position of the Harang discontinuity in the ionospheric currents.Premidnight, substorm enhancements in the westward electrojet current are accompanied by precipitation‐enhanced Hall conductivity but little change in the convection electric field. At lower latitudes, the region of strong sunward convection (and northward electric field) is displaced equatorward during the substorm. As a result, the electric field increases as the eastward current increases at previously subauroral latitudes during the substorm. After midnight, enhancements in the electric field magnitude and the Hall conductivity alternate in supporting the substorm enhanced currents.
Precise relocations of earthquakes and seismotectonics of the New Hebrides Island Arc
Authors: Pascal Georges , Isacks Bryan L. , Barazangi Muawia , Dubois Jacques 
Published: February 2008

Earthquakes for the period 1962–1973 are relocated by the method of joint hypocenter determination in order to resolve better the configuration and structure of the inclined seismic zone in the New Hebrides island arc. Twelve new focal mechanism solutions are reported and, together with previously published solutions, are integrated with the new information on the spatial distribution of hypocenters. At intermediate depths the seismic zone has a uniformly steep dip of about 70° and exhibits no resolvable contortions or disruptions along at least 700 km of the subduction zone. The thickness of the zone, about 20 km, may be in part due to seismically active fault zones which cut across a portion of the descending lithosphere. Features associated with the anomalous central region of the arc, where the d'Entrecasteaux fracture zone is being subducted and where the islands of Santo and Malekula appear to be in positions normally occupied by the oceanic trench, include the following: (1) an inclined zone of shallow earthquakes with very much smaller dip than is found elsewhere in the arc, (2) a pronounced gap in seismic activity at depths between about 50 and 120 km, (3) evidence for features in the upper or overthrust plate with trends transverse to the arc and parallel to the east‐west trends of the topographic feature being subducted, including nodal planes of shallow focal mechanism solutions, and (4) two features which appear to coincide with the downdip projection of the northern scarp of the d'Entrecasteaux fracture zone, including a well‐defined boundary between two adjacent zones of plate slippage along the main plate boundary and a faultlike feature in the intermediate depth seismic zone which also has a strike parallel to the fracture zone.Appendix table and entire article are available on microfiche.Order from American Geophysical Union, 1909 K Street, N.W.,Washington, D. C., 20006. Document J78‐006; $1.00. Payment mustaccompany order.