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  • Articles  (43)
  • 1990-1994  (27)
  • 1985-1989  (16)
  • 1935-1939
  • Geosciences  (43)
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  • Articles  (43)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 123 (1985), S. 610-623 
    ISSN: 1420-9136
    Keywords: Radiative-convective model ; Cloud feedback ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The effect of cloud feedback on the response of a radiative-convective model to a change in cloud model parameters, atmospheric CO2 concentration, and solar constant has been studied using two different parameterization schemes. The method for simulating the vertical distribution of both cloud cover and cloud optical thickness, which depends on the relative humidity and on the saturation mixing ratio of water vapor, respectively, is the same in both approaches, but the schemes differ with respect to modeling the water vapor profile. In scheme I atmospheric water vapor is coupled to surface parameters, while in scheme II an explicit balance equation for water vapor in the individual atmospheric layers is used. For both models the combined effect of feedbacks due to variations in lapse rate, cloud cover, and cloud optical thickness results in different relationships between changes in surface temperature, planetary temperature, and cloud cover. Specifically, for a CO2 doubling and a 2% increase in solar constant, in both models the surface warming is reduced by cloud feedback, in contrast to no feedback, with the greater reduction in scheme I as compared to that of scheme II.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Contributions to mineralogy and petrology 116 (1994), S. 365-380 
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Chemical data of 39 fresh basaltic glasses from the East Pacific Rise (EPR) between 6 and 30°S and Pb, Sr, and Nd isotopic compositions of 12 basalt glasses are presented. Major and trace element data indicate a wide compositional range, including primitive basalts (Mg#=0.67) and highly evolved FeTi-basalts (Mg#=0.34) [molMg/(Mg+Fe2+)]. The compositional range can be attributed to low-pressure fractional crystallization. Fractionation-corrected major element concentrations provide evidence for varying mantle melting conditions. Calculations of the melting conditions suggest melt generation in a rising upper mantle column between 20 and 10 kbar, at temperatures between 1430 and 1280°C, and total degrees of partial melting between 17 and 20% by weight. Leached and hand-picked basalt glasses display large variations in 87Sr/86Sr (0.70235–0.70270), 143Nd/144Nd (0.51312–0.51323), and 206Pb/204Pb (18.064–18.665), but are similar to other N-type MORB from the EPR. The isotopic ratios of basalts from 13 to 23°S show strong correlations and delineate two systematic trends. From 23 to 17°S, 87Sr/86Sr and Pb isotope ratios increase and 143Nd/144Nd decrease in agreement with previous results (Mahoney et al. 1989). A reverse trend is indicated by basalts from 17 to 13°S. However, K/Ti and (La/Sm)N continuously increase from 23 to 13°S. This opposite behavior indicates a recent decoupling of isotopic and minor element ratios in the mantle between 13 and 17°S. North of 13.5°S (Garrett Fracture Zone), isotopic data show no systematic variation with ridge location and display an overall weaker covariation. The results suggest that the isotopic variations and ridge segmentation appear to be unrelated and that major ridge offsets apparently coincide with changes in mantle melting conditions (P, T, F) (F, degrees of melting). There is no evidence for a systematic relationship between calculated melting conditions and second order ridge segmentation. Our isotopic data provide further evidence for regionally confined chemical variations in the mantle at 5 to 30°S. We interpret the isotopic trends as reflecting melting of distinct smallvolume and old enriched mantle components. In contrast, variations in trace elements are attributed to young mantle differentiation processes.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Environmental geology 24 (1994), S. 1-6 
    ISSN: 1432-0495
    Keywords: Nitrate ; Groundwater ; Modeling ; Denitrification ; Nitrogen balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Implemented on behalf of the Federal Ministry for Research and Technology (BMFT), a model is developed to trace the nutrient flow of nitrate in the soil and the groundwater on a supraregional scale. Research work is intended to indicate regionally differentiated hazardous potentials and thereby provide a basis for recommending comprehensive measures to protect groundwater in Germany. The adaption of the model to the hydrogeological and agricultural conditions of other states is possible in principle. This article focuses on the hydrogeological model parts. A high nitrate pollution of groundwater can be expected in all regions with intensive agricultural use of the topsoil. In particular, groundwater in solid rock areas is susceptible to nitrate pollution. There a rapid groundwater turnover and thus a short residence time for the groundwater in the aquifer is typical. Oxidizing aquifer conditions usually prevail in solid rock aquifers, preventing nitrate degradation. In many loose rock areas, in contrast, the groundwater has a low flow velocity and a long residence time in the aquifer. Because of a lack of free oxygen, a complete degradation of nitrate can occur, as long as iron sulfide compounds and/or organic carbon are available in the aquifer. A more detailed presentation of the whole research work is given in Wendland et al. (1993).
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A simple exponential expression, based upon a form of the Kazanski-Monin stability parameter, modified to account explicitly for effects of surface roughness, and semi-empirically derived from both qualitative and quantitative observations, is presented that relates windspeed and sensible heat flux density to Pasquill stability class. The method, though simple in mathematical form, gives results consistent with physical intuition and reproduces, quantitatively, the essential features of previously published nomograms with an added capability for treating all stability classes and any surface roughness from 0.10 to 100 cm. For the stable classes, a new expression for the wind profile stability factor, predicted by similarity theory, is introduced that produces results more consistent than the more common linear form.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Climatic change 16 (1990), S. iii 
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Climatic change 27 (1994), S. 147-160 
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This editorial essay conveys a clear message: The overuse of our fossil fuel resources especially in the North, and the overpopulation in many parts of the South, result in an unacceptable stress to Earth. This manifests itself in some of the most serious threats to mankind, such as global climatic change, environmental degradation, food shortage, hunger, poverty, and migration. It is the purpose of this editorial essay to make a contribution toward a reduction of some of these threats, notably those from climatic change. Specifically, I present a tractable climatic and environmental protection strategy which is designed to give concrete answers to such seemingly simple questions as: What has to be done? (This depends e.g. on the concentration stabilization objective of the Rio Climate Convention, and the global warming ceiling of the Enquete-Commission of the German Parliament). By whom does it have to be done? (This addresses the secret of a successful protection strategy which involves a fair burden sharing among the world's countries). When does it have to be done? (This discusses the problem of setting tractable, i.e. differentiated and binding emission targets). How can it be done? (This relates to individual countries, states, and municipalities. It is demonstrated for Germany how her commitment of a 25 to 30% CO2 reduction by 2005 can be achieved.) Moreover, the question is addressed: How many people and how much fossil fuel use can our planet stand? The major result is that without self-restraint climate and ecosystem protection cannot be maintained, because it is incompatible with trends in the wasteful fossil fuel use in the North and strong population growth in the South. Finally, a plea is made to share responsibility on the road toward a sustainable future.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Climatic change 3 (1990), S. 3-5 
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied climatology 49 (1994), S. 103-118 
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary In this paper we briefly describe the characteristics and the performance of our 1-D Muenster Climate Model. The model system consists of coupled models including gas cycle models, an energy balance model and a sea level rise model. The chemical feedback mechanisms among greenhouse gases are not included. This model, which is a scientifically-based parameterized simulation model, is used here primarily to help assess the effectiveness of various plausible policy options in mitigating the additional man-made greenhouse warming and the resulting sea level rise. For setting priorities it is important to assess the effectiveness of the various measures by which the greenhouse effect can be reduced. To this end we take a Scenario Business-as-Usual as a reference case (Leggett et al., 1992) and study the mitigating effects of the following four packages of measures: The Copenhagen Agreements on CFC, HCFC, and halon reduction (GECR, 1992), the Tropical Forest Preservation Plan of the Climate Enquete-Commission of the German Parliament on CO2 reduction (ECGP, 1990), a detailed reduction scheme for energy-related CO2 (ECGP, 1990), and a preliminary scheme for CH4, CO, and N2O reduction (Bach and Jain, 1992–1993). The required reduction depends, among others, on the desired climate and ecosystem protection. This is defined by the Enquete-Commission and others as a mean global rate of surface temperature change of ca. 0.1 °C per decade — assumed to be critical to many ecosystems — and a mean global warming ceiling of ca. 2 °C in 2100 relative to 1860. Our results show that the Copenhagen Agreements, the Tropical Forest Preservation Plan, the energy-related CO2 reduction scheme, and the CH4 and N2O reduction schemes could mitigate the anthropogenic greenhouse warming by ca. 12%, 6%, 35%, and 9% respectively. Taken together, all four packages of measures could reduce the man-made greenhouse effect by more than 60% until 2100; i.e. over the climate sensitivity range 2.5 °C (1.5 to 4.5) for 2 × CO2, the warming could be reduced from 3.5 °C (2.4 to 5.0) without specific measures to 1.3 °C (0.9 to 2.0) with the above packages of measures; and likewise, the mean global sea level rise could be reduced from 65 cm (46 to 88) without specific measures to 32 cm (22 to 47) with the above measures. Finally, the model results also emphasize the importance of trace gases other than CO2 in mitigating additional man-made greenhouse warming. According to our preliminary estimates, CH4 could in the short term make a sizable contribution to the reduction of the greenhouse effect (because of its relatively short lifetime of 10 yr), as could N2O in the medium and long term (with a relatively long lifetime of 150 yr).
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied climatology 38 (1987), S. 222-233 
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Zusammenfassung Der Einfluß von unterschiedlichen Aerosolen auf Klimaprozesse wird mit Hilfe eines zweidimensionalen Klimamodells untersucht. Um die zeitliche und räumliche Variabilität von Aerosolverteilungen zu berücksichtigen, wird über dem Meer ein überwiegend streuendes Aerosol und über Land ein überwiegend absorbierendes Aerosol in der Schicht zwischen dem Erdboden und dem 700 mb Niveau betrachtet. Der Einfluß von Aerosolen, Gasen und Wolken auf den Strahlungstransport wird mit Hilfe einer parametrisierten Zweistromapproximation berechnet. Aerosole verursachen eine Reduzierung der solaren Absorption an der Erdoberfläche und eine Verstärkung der atmosphärischen Absorption. Resultierende Änderungen der Klimamodellparameter sind nicht nur eine Funktion der strahlungsaktiven atmosphärischen Bestandteile, sondern auch von verstärkenden oder dämpfenden Rückkopplungsprozessen. Für die hier benutzten speziellen Aerosoltypen und die Verteilung der optischen Dicke nach Potter and Cess ergibt sich eine Änderung in der Jahresmitteltemperatur von −2,1 °C unter Berücksichtigung des Eis-Albedo-Rückkopplungseffekts. Ohne diesen Mechanismus beträgt die entsprechende Temperaturänderung −1,4 °C. In der Atmosphäre ergibt sich ebenfalls eine Temperaturabnahme in allen Breiten.
    Notes: Summary The response of climate processes to changes in aerosols is investigated using a two-dimensional zonally-averaged climate model. To account for the spatial and temporal heterogeneities of aerosol distributions, a strongly scattering maritime aerosol over ocean and a strongly absorbing rural aerosol over land are used in the layer between the surface and the 700 mb level. The effects of aerosols, gases and clouds on the radiative transfer are computed concurrently using a parameterized form of a two-stream approximation. Aerosols induce a reduction of the solar absorption at the surface and an enhancement of atmospheric absorption. The resulting changes in the climate model parameters are not only a function of the radiatively-active atmospheric constituents, but also of the amplifying or dampening effects of feedback processes employed in the model calculations. For the specified aerosol types and the optical thickness distribution given by Potter and Cess, the annual temperature change at the surface is −2.1 °C with ice-albedo feedback. Without ice-albedo feedback the corresponding value is −1.4 °C. In the present study aerosols produce a cooling effect in the atmosphere at all latitudes.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 1992-01-01
    Print ISSN: 0361-5995
    Electronic ISSN: 1435-0661
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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