共查询到20条相似文献，搜索用时 31 毫秒
1.
A box and a Gaussian plume model including gas-phase photochemistry and with plume dispersion parameters estimated from the few available plume observations are proposed and used for evaluation of photochemical transformations of exhausts from a single subsonic transport aircraft. The effects of concentration inhomogeneities in the plume cross section on the photochemical sources and sinks in the plume are analyzed for various groups of compounds. The influence of these inhomogeneities on the rate and on the mass of ambient air entrainment into the plume are studied also by comparing the box and the Gaussian plume model simulations during the first hours of their life. Due to the enterance of HOX and NOX from ambient air into the plume with rates varying from the wind shear and turbulence conditions, the rate of emitted NOX oxidation in the plume is dependent on these and also on the background concentration levels of HOX and NOX. 相似文献
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Summary The paper deals with the testing of the cloud top entrainment hypothesis. The method is based on the works by Warner[1–3], Paluch[4] and Telford[5]. The levels at which the entrained air might originate were determined. Several types of successions of entrainment levels were found; in the upper parts of cumuli, entrainment from above the level of observation prevailed.
mumunma uu ¶rt;a a u. m¶rt; nuam a am aa[1–3], a[4] u ¶rt;a[5]. n¶rt;uu u m¶rt;a ¶rt; nou¶rt;um. u a¶rt; mu muna n¶rt;am m u; a aa na¶rt;am u .相似文献
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D. A. Tanner 《Pure and Applied Geophysics》1972,97(1):111-126
Summary In a recent paperHunt andTanner [3]2) investigated the waves generated by a steadily moving two-dimensional pressure distribution, which was zero ahead of the disturbance and a constantp
0, tehind it, these regions being joined smoothly by a cubic function. Only those solutions with supercritical flow in both regions were considered, these were found to lead to an asymmetric solitary wave.This result is now extended to take account of the possibility of subcritical flow in either or both the regions, that is when there is a cnoidal wave train either behind and or ahead of the main solitary wave crest.The wave profiles are determined by the iterative method employed in the previous paper. This together with the wave drag associated with each system is computed for various values ofp
0/U
2, where is the fluid density andU a typical velocity. 相似文献
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ma n n¶rt;u u¶rt; u, m um u umuu ¶rt; amaa n nu , a¶rt;a n n a m. am nua ¶rt;a aau a¶rt;u n uumaa u ummna a ¶rt;u amuu 1965–1970
. mama u¶rt;, m na an amua ¶rt;mam ¶rt; m, m um n¶rt;um ¶rt;mam mm. 相似文献
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Linear stacking procedures are used to retrieve the attenuation of 91 modes belonging to the 3rd, 4th and 5th Rayleigh overtones branches in the 80–160 s period range, and contributing to the so-called PhaseX wave group. Our data show in general slightly less attenuation than expected from available models. Data space inversion shows that, when combined with previously measured fundamental modeQ's, this new dataset improves resolution significantly in the 1000–2000 km depth range. Based on this remark, we carry out a number of parameter space inversions. Our results suggest a narrow (80–200 km) zone of high attenuation (Q
=75–90), low attenuation in the intermediate mantle (670–1500 km); (Q
350), and lower values in the deeper mantle (Q
200). 相似文献
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D. W. Collinson 《Surveys in Geophysics》1984,7(1):57-73
The characteristics of the remanent magnetism of lunar samples suggests that it was acquired in a magnetic field on the Moon. The most likely origin of the field is a dynamo process in a molten, electricallyconducting core, but generation of a transient magnetic field during large meteorite impacts cannot be entirely ruled out. The magnetizing process may be thermoremanence, acquired when the rocks cooled through, the Curie point of the constituent iron grains which carry the remanent magnetization, or it may involve shock at the time of a meteorite impact, with or without a partial thermoremanence arising from heating.Evidence from absolute and relative determinations of the ancient field strength from the sample magnetizations strongly favours a global lunar field. This is implied by a trend which shows the field rising to a maximum value of 100 T between about 3.9–3.7 by ago and then decaying to 5–10 T until3.1 by. Such a systematic variation of field with time is not expected to be derived from magnetizations acquired in transient, impact-generated fields varying randomly in intensity.Contributory evidence for a dynamo field is provided by measurements of present lunar surface fields, the present very small dipole moment of the Moon and accumulating evidence of variation of the axis of the lunar field with time. Although there is no direct evidence for the existence of a lunar core the relevant observations are consistent with the presence of a core of up to 400 km, in radius. There are some difficulties associated with the lunar dynamo mechanism and its energy source but the evidence for a lunar dynamo is accumulating, with important implications for the structure and thermal history of the Moon. 相似文献
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Tikhonov A. I. Russkikh A. V. Moralev G. V. Golitsyn M. S. Vasil'ev A. V. Duev D. S. Timonova V. A. Nikolaev A. K. Lemeshko A. P. 《Water Resources》2004,31(6):673-678
Uranium-isotopic and multi-element hydrogeochemical methods are used to assess the natural pollution of fresh groundwater in horizons under development due to a modern intrusion of hypogene water with increased boron and fluorine contents in zones of old tectonic dislocations. The total index of the abovestandard (>MAC) pollution of groundwater in the region of the city of Kirov (the Kirov area) reaches 15. To reduce the effect of natural groundwater pollutants on the health of population, it is recommended that the groundwater intake should be regulated, purifiers should be used, and prospects revealed by the isotopic-and-hydrogeochemical data should be explored. The feasibility of modeling the groundwater formation and tracing the neotectonic dislocations in geological platforms is shown. 相似文献
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Santschi Peter H. Honeyman Bruce D. Quigley Matthew S. 《Aquatic Sciences - Research Across Boundaries》1993,55(4):230-239
In 1975 Paul Schindler produced the first oceanic trace metal scavenging model to explicitly include the role of surface chemistry as a control on trace metal water column residence times. The eighteen years that have elapsed since the publication of Schindler's seminal paper have seen the development of a variety of oceanic scavenging models; yet, the fundamental insight of his Zero-order Model remains the benchmark. This paper describes the role of Paul Schindler's work on surface chemistry in providing a framework for the current generation of trace element scavenging models. 相似文献
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Gary E. Thomas Charles A. Barth Elaine R. Hansen Charles W. Hord George M. Lawrence George H. Mount Gary J. Rottman David W. Rusch A. Ian Stewart Ronald J. Thomas Julius London Paul L. Bailey Paul J. Crutzen Robert E. Dickinson John C. Gille Shaw C. Liu John F. Noxon Crofton B. Farmer 《Pure and Applied Geophysics》1980,118(1):591-615
The 1981–82 Solar Mesosphere Explorer (SME) mission is described. The SME experiment will provide a comprehensive study of mesospheric ozone and the processes which form and destroy it. Five instruments will be carried on the spinning spacecraft to measure the ozone density and its altitude distribution from 30 to 80 km, monitor the incoming solar ultraviolet radiation, and measure other atmospheric constituent which affect ozone. The polar-orbiting spacecraft will be placed into a 3pm-3 am Sun-synchronous orbit. The atmospheric measurements will scan the Earth's limb and measure: (1) the mesospheric and stratospheric ozone density distribution by inversion of Rayleigh-scattered ultraviolet limb radiance, and the thermal emission from ozone at 9.6 m; (2) the water vapor density distribution by inversion of thermal emission at 6.3 m; (3) the ozone photolysis rate by inversion of the O2(1g) 1.27 m limb radiance; (4) the temperature profile by a combination of narrow-band and wide-band measurements of the 15 m thermal emission by CO2; and, (5) theNO2 density distribution by inversion of Rayleighscattered limb radiance at 0.439 m. The solar ultraviolet monitor will measure both the 0.2–0.31 m spectral region and the Lyman-alpha (0.1216 m) contribution to the solar irradiance. This combination of measurements will provide a rigorous test of the photochemical equilibrium theory of the mesospheric oxygen-hydrogen system, will determine what changes occur in the ozone distribution as a result of changes in the incoming solar radiation, and will detect changes that may occur as a result of meteorological disturbances. 相似文献
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J. J. Martin P. K. Wang H. R. Pruppacher A. E. Hamielec 《Pure and Applied Geophysics》1980,118(2):1109-1129
A theoretical model is presented which allows computing the efficiency with which aerosol particles of radius 0.1r10 m are collected by simple ice crystal plates of radius 50a
c
640 m in air of various relative humidities, temperatures and pressures. Particle capture due to thermophoresis, diffusiophoresis and inertial impaction are considered. It is shown that the capture efficiency of an ice crystal in considerably affected by phoretic effects in the range 0.1r1 m. For aerosol particles ofr>1 m the efficiency is strongly controlled by the flow field around the crystal and the density of the aerosol material. Trajectory analysis also predicts that aerosol particles are preferentially captured by the ice crystal rim. Our theoretica results are found to agree satisfactorily with the laboratory studies presently available. Comparison shows that for the same pressure, temperature and relative humidity of the ambient air ice crystal plates are better aerosol particle scavengers than water drops. 相似文献
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MAGSAT data and Curie-depth below Deccan flood basalts (India) 总被引：3，自引：0，他引：3
Ground and airborne magnetic data are severely disturbed due to random susceptibility variations in Deccan flood basalts. However, Magnetic Satellite (MAGSAT) data over the Deccan flood basaltic region of the Indian subcontinent exhibit filtering of surficial noise. Three passes over Deccan traps show a low at about 20°N latitude and a high at about 23°N latitude. Spectral analysis of these passes and an available 2-D MAGSAT vertical intensity map indicate a deep (40±4 km) magnetic interface. It is interesting to note that the determination of Curie-depth from MAGSAT matches and confirms the geothermal data model. The estimates correspond to the Moho depth derived from gravity and deep seismic sounding studies. The study suggests a continental shield-like geothermal gradient of about 14°C/km below the area. 相似文献
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Summary Using methods of numerical modelling of the propagation of ULF waves through the ionosphere, the characteristics of the vertical flux of electromagnetic energy are analysed in the ULF range — at the outer boundary of the modelled ionosphere (altitude 1000 km) the reflexibility and penetrability of the energy, at the Earth's surface the transmissivity of the energy. The existence of two frequency bands is proved within the ULF range with different forms of ionospheric wave filtration: a) The band of extremely low frequencies, f<0.1–0.2 Hz (pc3–5 and Pc2 pulsation ranges) with a mirroring effect of the ionosphere-Earth system, but with small absorption; b) the band f>0.2 Hz (the Pc1 range) with increased absorption, but with resonance windows and wave emissions with a very well defined frequency structure. 相似文献
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The integration of terrain computer modeling with field methods may provide a powerful mechanism for understanding active faults geometry, kinematics and long-term fault behavior. Radar interferometry was used on ERS tandem images to create a geocoded DEM (InSAR-DEM) with a nominal 20-m spatial-resolution of the central Apennines axial zone, a seismically active area characterized by historical destructive earthquakes with M 7. The potential was tested of InSAR-DEM application to the Fucino and Sulmona basin boundary faults, which have well-defined seismological, paleoseismological and/or geological evidence for their having seismogenic sources. In particular, slope maps extracted from the InSAR-DEM were used for fault scarps detection, whether on carbonate bedrock (fault scarp type 2) or affecting continental deposits within the basin (fault scarp type 1), and compared with the available geological and new field data. In order to assess the DEM accuracy and to evaluate morphometric parameters related to the long-term slip-rates of the faults, a set of topographic profiles was extracted from the InSAR-DEM and compared with analogous profiles derived from the available topographic map (i.e., 1/25,000, with 25 m contour interval). In particular, the use of InSAR-DEM analyses showed its better results, with respect to the standard topography, for urban/agricultural gently sloped areas where fault scarps affected unconsolidated and particularly soft sediments (e.g., Fucino basin fault systems), while in severely sloped carbonate ridge and forested areas low coherences and layover effects made InSAR-DEM application problematic. A maximum value of 1.1 ± 0.2 mm yr–1 slip-rate was obtained for the Fucino boundary fault. Finally, the recognized en-échelon pattern of the Sulmona basin boundary fault, provided a segmentation model for this structure corroborated by geological-structural field data. 相似文献