Improved ocean-geoid resolution from retracked ERS-1 satellite altimeter waveforms   总被引：6，自引：0，他引：6  

Stefan Maus  Chris M. Green  & J. Derek Fairhead 《Geophysical Journal International》1998,134(1):243-253

The ocean geoid can be inferred from the topography of the mean sea surface. Satellite altimeters transmit radar pulses and determine the return traveltime to measure sea-surface height. The ERS-1 altimeter stacks 51 consecutive radar reflections on board the satellite to a single waveform. Tracking the time shift of the waveform gives an estimate of the distance to the sea surface. We retrack the ERS-1 radar traveltimes using a model that is focused on the leading edge of the waveforms. While earlier methods regarded adjacent waveforms as independent statistical events, we invert a whole sequence of waveforms simultaneously for a spline geoid solution. Smoothness is controlled by spectral constraints on the spline coefficients. Our geoid solutions have an average spectral density equal to the expected power spectrum of the true geoid. The coherence of repeat track solutions indicates a spatial resolution of 31  km, as compared to 41  km resolution for the ERS-1 Ocean Product. While the resolution of the latter deteriorates to 47  km for wave heights above 2  m, our geoid solution maintains its resolution of 31  km for rough sea. Retracking altimeter waveform data and constraining the solution by a spectral model leads to a realistic geoid solution with significantly improved along-track resolution.  相似文献   

A formula describing both magnetic and isotopic blocking temperatures     

Derek York 《Earth and Planetary Science Letters》1978,39(1):89-93

The following new theorem is proved: the equation E/RT_B =ln(1.781 k₀τ), where E = activation energy, R = the molar gas constant and T_B = blocking temperature, applies equally well to both the isotopic and the magnetic systems in rocks from a cooling orogen. The isotopic model involves first-order loss of daughter, while the magnetic model applies to an assemblage of single-domain grains with constant E. Dodson supplied the original proof that the equation applied to isotopic systems. The well-known superficial similarity between the concepts of isotopic and magnetic blocking is thus given quantitative expression.  相似文献   

Aims and implementation in British urban and regional planning     

Derek R. Diamond 《Geoforum》1979,10(3):275-282

Failure to fully understand or recognise crucial but culturally-determined British dimensions has led to confusion and error even among the British geographers in understanding and contributing to, urban and regional planning. This point assumes more rather than less significance in the context of a discussion between British and Soviet geographers. This paper therefore examines in part one, three fundamental features of the British system of urban and regional planning and then proceeds in part two to focus on the aims and their implementation. It concludes with a reference to the nature of the relationship between planning and geography.  相似文献   

A two-dimensional photochemical model of the stratosphere with Rayleigh scattering     

Guido Visconti  Gianni Pitari  Derek Cunnold 《Pure and Applied Geophysics》1980,118(2):1033-1051

Computations of concentrations of minor stratospheric gases using a two-dimensional model of the stratosphere are reported. The model includes Rayleigh scattering. This results in an increase in the photodissociation rate computation time by a factor of 1.5. The effect of ground albedo is assessed by comparing our results with a calculation of photolysis rates for a constant albedo with latitude. Comparison of results with a reference model including only molecular absorption are also made. The largest differences (50%) occur in NO and OH. An approximate expression for including the effects of Rayleigh scattering and surface reflectance in multi-dimensional models is suggested.  相似文献   

Stable isotope studies of fluid inclusions in speleothems and their paleoclimatic significance     

Henry P Schwarcz  Russell S Harmon  Peter Thompson  Derek C Ford 《Geochimica et cosmochimica acta》1976,40(6):657-665

Fluid inclusions found trapped in speleothems (cave deposited travertine) are interpreted as samples of seepage water from which enclosing calcium carbonate was deposited. The inclusions are assumed to have preserved their D/H ratios since the time of deposition. Initial ¹⁸O/¹⁶O ratios can be inferred from δD because rain- and snow-derived seepage waters fall on the meteoric water line (δD = 8δ¹⁸O + 10). Estimates of temperature of deposition of the carbonate can be calculated from inclusion D/H ratios and δ¹⁸O of enclosing calcite in Pleistocene speleothems. For most speleothems investigated (0–200,000 yr old) δ¹⁸O of calcite appears to have decreased with increasing temperature of deposition indicating that the dominant cause of climate-dependent change in δ¹⁸O of calcite was the change in K_cw, the isotope fractionation equilibrium constant, with temperature; δ¹⁸O of meteoric precipitation generally increased with increasing temperature, but not sufficiently to compensate for the decrease in K_cw.  相似文献   

Volcanoes and Impact Craters on the Moon and Mars: by Piero Leonardi with the collaboration of A. Rittmann and E. Sommavilla. Elsevier, Amsterdam, 1976, 463 pp.; Dfl. 155.00 (ca. U.S. $59.75)     

Derek Bostok 《Journal of Volcanology and Geothermal Research》1977,2(4):397-398

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The erosion history of Shetland: a review     

Derek Flinn 《Proceedings of the Geologists' Association. Geologists' Association》1977,88(3):129-146

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Nature's bounty     

Derek Bears 《Meteoritics & planetary science》1998,33(Z4):A3-A3

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First cosmogenic 10Be age constraint on the timing of Younger Dryas glaciation and ice cap thickness,western Scottish Highlands     

Nicholas R. Golledge  Derek Fabel  Jeremy D. Everest  Stewart Freeman  Steven Binnie 《第四纪科学杂志》2007,22(8):785-791

We use cosmogenic ¹⁰Be surface exposure age techniques at a locality close to Rannoch Moor, western Scottish Highlands, in order to establish the age and chronology of its most recent glaciation. Glacial erratics and an in situ bedrock quartz vein sampled from this site—the summit of Beinn Inverveigh—have yielded zero‐erosion exposure ages of 12.9 ± 1.5 ka to 11.6 ± 1.0 ka, implying complete ice cover of the mountain during the Younger Dryas, or Loch Lomond Stadial. These results fit closely with published ¹⁴C dates that bracket the maximum (lateral) extent of ice cap outlet glaciers, and are the first internally consistent ages to specifically address this period of glaciation in Scotland. Furthermore, the dates imply that previous palaeoglaciological reconstructions for this area may have underestimated both the thickness of the former ice cap and, by implication, its volume. © British Geological Survey/Natural Environment Research Council copyright 2007. Reproduced with the permission of BGS/NERC. Published by John Wiley & Sons, Ltd.  相似文献   

Determination of trajectories of metallic spheres settling in non-newtonian fluids     

Derek D.  Lichti  Monica M.  Gumulya  Richard R.  Horsley 《The Photogrammetric Record》2009,24(125):37-50

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