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  • 1
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    In:  Geological Society Special Publication 240: 179-193.
    Publication Date: 2007-10-08
    Description: Physical properties of gabbroic samples from Ocean Drilling Program Hole 1105A were measured in the laboratory, with a particular emphasis on the analysis of electrical properties. This data-set includes the major lithologies sampled in ODP Hole 1105A: gabbros, olivine gabbros, oxide-rich gabbros, and, for all rock types, different ranges of alteration were sampled: from fresh to highly altered. All these lithologies correspond to the seismic Layer 3 layer of the oceanic crust, and large-scale geophysical data interpretation requires a complete understanding of the physical properties of rocks in this section. Electrical conductivities measured on brine-saturated gabbros reveal strong excess conductivity for samples rich in oxide minerals and, to a lesser extent, for altered samples. However, the classical models do not explain the excess conductivity reported in the oxide-rich samples when saturated with brine. The electrical conduction via electronic processes in metallic minerals has been taken into account in our analysis of the electrical properties. The oxide minerals' contribution has been independently estimated through measuring dry electrical resistivity. These measurements allowed quantification of the electronic conduction, which can reach 80% of the full conductivity for the most oxide-rich gabbros.
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  • 2
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary An analysis of mesoscale gravity wave events during the severe weather outbreak in the Red River Valley on 10–11 April 1979 is presented utilizing surface pressure data and the 3 h rawinsonde data from the AVE-SESAMEI special network. The unique data set provided by the SESAME field experiment makes it possible to relate the wavelike characteristics observed at the surface to the variability of the temperature, humidity, and wind fields over a deep tropospheric layer that act to initiate and sustain the waves over long distances and time periods. Three different wave events (A, B, and C) were identified via spectral analysis and cross-correlation techniques. They all have similar periods, approximately 3 h, but different phase velocities. All three wave events are generated and propagate in the exit region or anticyclonic side of upperlevel jet streaks. Convection and wind shear are shown to be unlikely contributors to the generation of event A, which is probably related to the development of a strong divergent field in association with an upper-tropospheric jet streak and to the ensuing mass adjustment process. Events B and C also appear in a region of strong ageostrophic motion associated with an upper-level jet streak. However, the low values of the Richardson number (Ri) at the critical levels of these two waves suggest vertical wind shear as a likely contributor to their generation and/or maintenance. A linear stability analysis confirms, with unprecedent spatial and temporal resolution, that a modal structure is present in the atmosphere whose characteristics are consistent with those of waves B and C. Three-hourly rawinsonde data show strong temporal and spatial variability throughout the troposphere in the wind, temperature, and humidity fields when the waves are present. Convective systems, as detected by radar, are closely linked to the waves, although not in a consistent manner: cells intensify or develop at the passage of a wave trough in event A, at the passage of a wave ridge in event C, and at the passage of a wave trough or ridge in event B, depending on the geographic location of the cells. For all three events, maximum rainfall recorded at the surface is associated with a wave ridge with a time lag of approximately 1 h.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary This paper describes the evolution of two thunderstorms which developed over northeastern Colorado on 23 July 1983, and more significantly discusses the possible causal relationship between them. In particular, a disturbance apparently created by the first thunderstorm, which developed over the eastern slopes of the Rocky mountains, seems to have triggered the second thunderstorm, which developed further east over the high plains. We present evidence that suggests that the disturbance is a rapidly propagating gravity wave (possibly a solitary wave of depression) that occupied most of the troposphere and was generated by the explosive convective development of the first thunderstorm. Detailed observations of the interactions between these two storms were possible because both storms developed over a dense network of automated weather stations that provided high temporal and spatial resolution surface measurements of pressure, temperature, precipitation, and horizontal wind velocity. Also located within this mesonetwork was a high power 915 MHz wind profiler that provided radial velocities throughout most of the troposphere. These measurements were supplemented with GOES visible and infrared satellite imagery and operational data from National Weather Service rawinsondes and weather radars.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2016-09-08
    Description: Sampling an intact sequence of oceanic crust through lavas, dikes, and gabbros is necessary to advance the understanding of the formation and evolution of crust formed at mid-ocean ridges, but it has been an elusive goal of scientific ocean drilling for decades. Recent drilling in the eastern Pacific Ocean in Hole 1256D reached gabbro within seismic layer 2, 1157 meters into crust formed at a superfast spreading rate. The gabbros are the crystallized melt lenses that formed beneath a mid-ocean ridge. The depth at which gabbro was reached confirms predictions extrapolated from seismic experiments at modern mid-ocean ridges: Melt lenses occur at shallower depths at faster spreading rates. The gabbros intrude metamorphosed sheeted dikes and have compositions similar to the overlying lavas, precluding formation of the cumulate lower oceanic crust from melt lenses so far penetrated by Hole 1256D.
    Type: Article , PeerReviewed
    Format: text
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Flow, turbulence and combustion 24 (1971), S. 422-430 
    ISSN: 1573-1987
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The hydrodynamic equations governing the propagation of waves in one dimension are solved by successive approximations. Secular terms appear in a regular perturbation analysis, which limit the practical usefulness of such an approach. Two singular perturbation methods are described to remedy the presence of singularities. It is shown that the Poincaré-Linghthill-Kuo method and the method of characteristics are equivalent at least to first order in the amplitude of the perturbed velocity.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 117 (1978), S. 627-663 
    ISSN: 1420-9136
    Keywords: Gravity waves ; Tropospheric dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The nature and the role of gravity waves in the troposphere is briefly discussed and reviewed. After describing some basic properties of gravity waves and their generation mechanisms, we analyze their ability to influence phase changes, trigger and organize convective cells, to produce and interact with turbulence, and to affect diffusive processes in the atmosphere. Throughout, the emphasis is placed on the physical processes involved in the interaction of gravity waves with mesoscale and planetary boundary layer phenomena. Also discussed and reviewed are those remote sensing devices which are particularly useful in revealing and measuring such waves. Finally, an attempt is made to outline possible lines of future work for the purpose of fully understanding the role of gravity waves in mesoscale and microscale dynamics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The characteristics of waves excited in a stratified shear flow with a velocity profile monotonically increasing above the ground are calculated numerically. It is shown that unstable modes exist when the Brunt-Väisälä frequency of the ambient atmosphere decreases sufficiently fast with height. Their growth rates as a function of the horizontal wavelength and the local Richardson number are given, and a comparison between them and experimental data obtained for the night-time-boundary layer of the Earth's atmosphere is carried out. Finally, the characteristics of the singular neutral modes that the system can support are presented.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2017-06-09
    Description: Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 116 (2011): B07103, doi:10.1029/2010JB007931.
    Description: Expeditions 304 and 305 of the Integrated Ocean Drilling Program cored and logged a 1.4 km section of the domal core of Atlantis Massif. Postdrilling research results summarized here constrain the structure and lithology of the Central Dome of this oceanic core complex. The dominantly gabbroic sequence recovered contrasts with predrilling predictions; application of the ground truth in subsequent geophysical processing has produced self-consistent models for the Central Dome. The presence of many thin interfingered petrologic units indicates that the intrusions forming the domal core were emplaced over a minimum of 100–220 kyr, and not as a single magma pulse. Isotopic and mineralogical alteration is intense in the upper 100 m but decreases in intensity with depth. Below 800 m, alteration is restricted to narrow zones surrounding faults, veins, igneous contacts, and to an interval of locally intense serpentinization in olivine-rich troctolite. Hydration of the lithosphere occurred over the complete range of temperature conditions from granulite to zeolite facies, but was predominantly in the amphibolite and greenschist range. Deformation of the sequence was remarkably localized, despite paleomagnetic indications that the dome has undergone at least 45° rotation, presumably during unroofing via detachment faulting. Both the deformation pattern and the lithology contrast with what is known from seafloor studies on the adjacent Southern Ridge of the massif. There, the detachment capping the domal core deformed a 100 m thick zone and serpentinized peridotite comprises ∼70% of recovered samples. We develop a working model of the evolution of Atlantis Massif over the past 2 Myr, outlining several stages that could explain the observed similarities and differences between the Central Dome and the Southern Ridge.
    Keywords: Atlantis Massif ; Integrated Ocean Drilling Program ; Oceanic Core Complex
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 9
    Publication Date: 2011-08-24
    Description: On 21 December 1991 from approximately 1300 to approximately 1600 UTC a monochromatic wave train with an 8.2-min period was observed by the suite of instruments at the Flatland Atmospheric Observatory (FAO), located in very flat terrain near Champaign-Urbana, Illinois. A 915-MHz radar measured the vertical wind velocity w every 60 s from 0.55 km MSL (0.34 km AGL) to approximately 3 km with 250-m range gates, and a 50-MHz radar measured the oblique wind in four directions, as well as w, every 130 s from 2.75 to approximately 7.25 km with 750-m range gates. A meteorological ground station measured the surface pressure P, wind speed vector u and azimuth alpha, temperature, solar insolation, etc., every 30 s. P was also measured every 120 s by six digital barograph stations within 30 km of Flatland. Using the hodograph of surface vector u and alpha and the impedance relation, we estimated the azimuthal direction of propagation phi to be 45 deg +/- 15 deg clockwise from north, the intrinsic and apparent horizontal phase speeds C(sub i) and C(sub o), respectively, (which are about equal since the direction of propagation is about normal to the mean wind) to be 21 +/- 5 m/s, and the horizontal wavelength lambda to be 10.0 +/- 2.5 km. The peak-to-peak surface horizontal perturbation velocity varied from approximately 2 to 5 m/s from cycle to cycle.
    Keywords: COMMUNICATIONS AND RADAR
    Type: National Central Univ., Solar-Terrestrial Energy Program: Proceedings of the 6th Workshop on Technical and Scientific Aspects of MST Radar; p 200-204
    Format: text
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  • 10
    Publication Date: 2011-08-16
    Description: Small amplitude nonlinear longitudinal plasma oscillations perturbation analysis, discussing Landau damping, monochromatic wave evolution and independent variable expansion
    Keywords: PHYSICS, PLASMA
    Type: ; BROTECHNIKA, NO. 2(
    Format: text
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