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  • GEOPHYSICS  (16)
  • gridded map  (1)
  • 1990-1994  (15)
  • 1975-1979  (2)
  • 1
    Digitale Medien
    Digitale Medien
    The renavigation of Sea Beam bathymetric data between 9° N and 10° N on the East Pacific Rise (1993)
    Springer
    Marine geophysical researches 15 (1993), S. 1-12 
    Details
    ISSN: 1573-0581
    Schlagwort(e): Sea Beam bathymetry ; renavigation ; gridded map ; East Pacific Rise
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract We present a gridded Sea Beam bathymetric map of a 5100 km2 area between 9° and 10° N on the East Pacific Rise (included as a color separate accompanying this issue). The raw bathymetric data are renavigated using a technique for calculating smooth adjustments to navigation that incorporates absolute constraints from satellite fixes and acoustically-located explosive shots, and relative constraints from the misfit of bathymetric data at ship track crossovers. We describe a back-projection technique for gridding the bathymetric data that incorporates an approximation for the power distribution within a narrow-beam echo sounding system and accounts for the variable uncertainties associated with multi-beam data. The nodal separation of the resulting map is ~ 80 m in both latitude and longitude, and the sampling of grid points within a 60 × 85 km2 region is in excess of 99%. A formal analysis of variance is applied to the gridded bathymetric data. For each grid point, the difference between the variance of data from within a track versus data from between tracks provides an upper bound on the magnitude of bathymetric misfits arising from navigational errors. The renavigation results in an 88% reduction in this quantity. We also examine the effects of renavigation on the misfit of magnetic and gravity data at crossovers and compare our results with other bathymetric surveys. A striking feature of the final bathymetric map is the sinuous regional shape of the rise axis. In plan view, the local trend of morphology sometimes varies by up to 15° and the distances separating changes in morphological trend are about 10–20 km. In cross section the slopes of the rise flanks are notably asymmetric and show some correlation with the offset of the axial magmatic system as detected by seismic methods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01204148
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  • 2
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    On the age of stratospheric air and ozone depletion potentials in polar regions (1992)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-24
    Beschreibung: Observations of the nearly inert, man-made chlorofluorocarbon CFC-115 obtained during January 1989 are used to infer the age of air in the lower stratosphere. These observations together with estimated release rates suggest an average age of high-latitude air at pressure altitudes near 17-21 km of about 3 to 5 yr. This information is used together with direct measurements of HCFC-22, HCFC-142b, CH3Br, H-1301, H-1211, and H-2402 to examine the fractional dissociation of these species within the Arctic polar lower stratosphere compared to that of CFC-11 and hence to estimate their local ozone depletion potentials in this region. It is shown that these HCFCs are much less efficiently dissociated within the stratosphere than CFC-11, lowering their ozone depletion potentials to only about 30-40 percent of their chlorine loading potentials. In contrast, the observations of CH3Br and the Halons considered confirm that they are rapidly dissociated within the stratosphere, with important implications for their ozone depletion potentials.
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 97; D12,; 12
    Format: text
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  • 3
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    A diagnostic for denitrification in the winter polar stratospheres (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: The pairwise correlation of NO(y) and N2O data from the Southern and Northern Hemispheres is presented. Both data sets show a linear correlation region, defined as a reference state, and regions of denitrification where the correlation breaks down. Using two-dimensional photochemical model simulations of the atmosphere, a similar linear correlation is found between NO(y) and N2O, thereby establishing a theoretical framework for the reference state. This general approach, which can be extended to other pairs of molecules, should prove to be powerful in further comparisons of aircraft data with numerical models.
    Schlagwort(e): GEOPHYSICS
    Materialart: Nature (ISSN 0028-0836); 345; 698-702
    Format: text
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  • 4
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    The polar stratospheric cloud event of January 24. II - Photochemistry (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: During the 1988/89 Airborne Arctic Stratospheric Expedition (AASE), observations of the chemical composition, aerosol characteristics and atmospheric state were obtained from two aircraft, a NASA ER-2 and a DC-8. This paper presents a diagnosis of observations obtained using the ER-2 on January 24, 1989, using a Lagrangian coupled microphysical-photochemical model. The high chlorine monoxide mixing ratios observed from the ER-2 on the afternoon of January 24, 1989 are interpreted as a result of in situ heterogeneous release of reactive chlorine from the reservoirs HCl and CIONO2 on type-1 polar stratospheric cloud particles observed to be present at that time. This essential element in theories of polar ozone depletion has never before been observed directly in the stratosphere.
    Schlagwort(e): GEOPHYSICS
    Materialart: Geophysical Research Letters, Supplement (ISSN 0094-8276); 17; 541-544
    Format: text
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  • 5
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    Simulating the evolution of the chemical composition of the 1988/89 winter vortex (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: During the 1988/89 Airborne Arctic Stratospheric Expedition (AASE) observations of the chemical composition and aerosol characteristics of the winter vortex were obtained from a NASA ER-2 aircraft. In this paper we present interpretations of observations obtained on three ER-2 flights using a Lagrangian coupled photochemical-microphysical model. It is argued that observations obtained on Jaunary 16 and 19, and February 10, represent different stages of the chemical evolution of the vortex, from the early stages of chlorine release, the onset of denitrification and the intensively processed state.
    Schlagwort(e): GEOPHYSICS
    Materialart: Geophysical Research Letters, Supplement (ISSN 0094-8276); 17; 549-552
    Format: text
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  • 6
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    The polar stratospheric cloud event of January 24, 1989. I - Microphysics (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Rapid adiabatic cooling induced by synoptic forcing led to polar stratospheric cloud (PSC) formation on January 24, 1989, at altitudes sampled by the ER-2 aircraft. Particle characteristics measured by the Forward Scattering Spectrometer Probe (FSSP) on the ER-2 were compared to those calculated using a theoretical PSC microphysics model. Although calculations were sensitive to local changes in cooling rate, generally favorable agreement was found, that in particle surface area being especially important since this parameter dictates heterogeneous chemical rates. The overall model performance suggests that the current approach for simulating Type 1 (nitric acid trihydrate) PSC formation under rapid cooling conditions is well founded and can be used to study the effects of heterogeneous chemistry on stratospheric composition.
    Schlagwort(e): GEOPHYSICS
    Materialart: Geophysical Research Letters, Supplement (ISSN 0094-8276); 17; 537-540
    Format: text
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  • 7
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    On the influence of polar stratospheric cloud formation on chemical composition during the 1988/89 Arctic winter (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: The northern winter polar vortex is more disturbed dynamically and warmer than the Antarctic equivalent, and correspondingly fewer polar stratospheric clouds (PSCs) are observed to form. However, the rapid flow of stratospheric air through slow moving synoptically forced PSC regions can result in exposure of both vortical and extra vortical air to PSCs intermittently throughout the winter months. This periodic exposure to PSCs may be sufficient to perturb the chemical composition of large volumes of nothern hemisphere air. The synoptic forcing also leads to marked meridional flow which has a profound effect on chemical composition, having major impacts on both short term ozone depletion and the longer term recovery to lower ClOx abundances. Accurate simulation of the air flow is thus essential for the reliable calculation of ozone loss in polar regions.
    Schlagwort(e): GEOPHYSICS
    Materialart: Geophysical Research Letters, Supplement (ISSN 0094-8276); 17; 545-548
    Format: text
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  • 8
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    Comparison of 2-D model simulations of ozone and nitrous oxide at high latitudes with stratospheric measurements (1992)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-24
    Beschreibung: A linear reference relationship between O3 and N2O has been used to estimate polar winter O3 loss from aircraft data taken in the lower stratosphere. Here, this relationship is evaluated at high latitudes by comparing it with a 2D model simulation and with NIMBUS 7 satellite measurements. Although comparisons with satellite measurements are limited to January through May, the model simulations are compared during other seasons. The model simulations and the satellite data are found to be consistent with the winter O3 loss analysis. It is shown that such analyses are likely to be inappropriate during other seasons.
    Schlagwort(e): GEOPHYSICS
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 97; 939-944
    Format: text
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  • 9
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    Homogeneous and heterogeneous chemistry along air parcel trajectories (1990)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The study of coupled heterogeneous and homogeneous chemistry due to polar stratospheric clouds (PSC's) using Lagrangian parcel trajectories for interpretation of the Airborne Arctic Stratosphere Experiment (AASE) is discussed. This approach represents an attempt to quantitatively model the physical and chemical perturbation to stratospheric composition due to formation of PSC's using the fullest possible representation of the relevant processes. Further, the meteorological fields from the United Kingdom Meteorological office global model were used to deduce potential vorticity and inferred regions of PSC's as an input to flight planning during AASE.
    Schlagwort(e): GEOPHYSICS
    Materialart: NASA, Washington, NASA Upper Atmosphere Research Program: Research Summaries 1988-1989; p 239-240
    Format: application/pdf
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  • 10
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    Observational and theoretical evidence in support of a significant in-situ photochemical source of tropospheric ozone (1979)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-27
    Beschreibung: The latitudinal and seasonal variation of ozone in the troposphere is discussed. Of particular interest is the asymmetrical behavior of this gas with respect to the two hemispheres. These asymmetries, when coupled with a diagnostic photochemical model of the troposphere, lends support to the view that ozone cannot be viewed as an inert tracer of stratospheric origin. In the calculations it is noted that it is likely that the budgets of carbon monoxide and tropospheric ozone may be quite dependent on each other and the calculations are discussed in light of the uncertainty which currently exists about representative global tropospheric background concentrations of the nitrogen oxides. In addition, the seasonal variation of excess (C-14)O2 (a stratospheric tracer) is examined and compared with the seasonal ozone variation during the same period of observations at the same location and altitudes. The distinct maxima for ozone found during the summer in the lower troposphere are not present for the (C-14)O2 data. This finding likewise suggests that photochemical processes taking place in the troposphere are an important source term for tropospheric ozone.
    Schlagwort(e): GEOPHYSICS
    Materialart: Tellus; 13; Oct. 197
    Format: text
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