On the effect of emissions from aircraft engines on the state of the atmosphere     

U. Schumann 《Annales Geophysicae》1994,12(5):365-384

Emissions from aircraft engines include carbon dioxide, water vapour, nitrogen oxides, sulphur components and various other gases and particles. Such emissions from high-flying global civil subsonic air traffic may cause anthropogenic climate changes by an increase of ozone and cloudiness in the upper troposphere, and by an enhanced greenhouse effect. The absolute emissions by air traffic are small (a few percent of the total) compared to surface emissions. However, the greenhouse effect of emitted water and of nitrogen oxides at cruise altitude is potentially large compared to that of the same emissions near the earth’s surface because of relatively large residence times at flight altitudes, low background concentrations, low temperature, and large radiative efficiency. Model computations indicate that emission of nitrogen oxides has doubled the background concentration in the upper troposphere between 40○N and 60○N. Models also indicate that this causes an increase of ozone by about 5-20%. Regionally, the observed annual mean change in cloudiness is 0.4%. It is estimated that the resultant greenhouse effect of changes in ozone and thin cirrus cloud cover causes a climatic surface temperature change of 0.01-0.1 K. These temperature changes are small compared to the natural variability. Recent research indicates that the emissions at cruise altitude may increase the amount of stratospheric aerosols and polar stratospheric clouds and thereby have an impact on the atmospheric environment. Air traffic is increasing about 5-6% per year, fuel consumption by about 3%, hence the effects of the related emissions are expected to grow. This paper surveys the state of knowledge and describes several results from recent and ongoing research.  相似文献   

Anreicherung von Metallionen durch Membranfiltration von Polyelektrolytkomplexen     

G. Schumann  R. Kümmel 《洁净——土壤、空气、水》1986,14(4):385-394

The separation of heavy metals by complexation with macromolecular water-soluble agents and subsequent ultrafiltration is described. The method can be expected to join common techniques of metal separation like liquid-liquid extraction, adsorption, redox reaction or liquid membrane permeation. Reactions between metal ions and polymer phases are characterized as pH-dependent distribution equilibria illustrated at a propene-maleic acid copolymer as an example. The complexation behaviour of the substance under study is governed by isotherms of the saturation type. Attempts proved to be successful to calculate break-through constants as well as saturation capacities from batch-type studies and dynamic measurements by transferring the laws of adsorption and ion exchange, respectively, to the ultrafiltration process. The quantities of fixed metals amounting to about 2.5 mmol/g were found to be in the range of moderate adsorbents. A solution consisting of 3 solutes has been tested to get more detailed information on mixture behaviour as compared to single component systems. In the long run, the proposed method should provide an additional variant for the extraction and concentration of metal ions from diluted aqueous solutions.  相似文献   

Measurements of atmospheric radon-220 using delayed alpha-particle coincidences     

J. Bogen  M. Sappok  Dr. G. Schumann 《Meteorology and Atmospheric Physics》1972,21(2-3):171-182

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Über die bevorzugte kristallographische orientierung der einzelkristalle in natürlichen faserhalitaggregaten     

Dr. U. Goeman  Prof. Dr. H. Schumann 《Mineralogy and Petrology》1976,23(2):137-150

Zusammenfassung Die Orientierung der Kristallite eines Faserhalites wurde mit einer Röntgen-U-Tisch-Methode bestimmt, indem für jedes Korn die drei Symmetrieachsen des durch einen Bildverstärker sichtbar gemachten Laue-Bildes zentral gestellt wurden. Die Darstellung der Ergebnisse erfolgte in einer flächentreuen Projektion durch Eintragung der Pole der Kornschnittflächen im entsprechenden Präparat in einem sphärischen Dreieck mit den Durchstoßpunkten der Senkrechten auf (001), (011) und (111) als Eckpunkten.Aus der Bearbeitung eines Schnittes senkrecht zur Faserrichtung ergibt sich, daß etwa ein Drittel der Kristallite eine zweizählige Achse nahe zur Faserrichtung hat; das entspricht qualitativ den Erwartungen aus den vektoriellen Wachstumsgeschwindigkeiten beim Halit. Die Ergebnisse aus Schnitten parallel zur Faserachse sind nicht so klar zu interpretieren, jedoch zeigen sich auch hier Orientierungseffekte.

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Preferred crystallographic orientation of crystallites in natural fibrous halite aggregates

Summary The orientations of the crystallites in a fibrous halite were determined using an X-ray universal stage method in which for each individual grain the Laue-diagrams of the three symmetry axes, made visible by an image intensifier, were set at the center. The results are presented in an equal-area net using the poles of the corresponding grain's sections in a spherical triangle with the normals to (001), (011) and (111) as corner points.Studies on a thin section perpendicular to the fiber direction revealed a two-fold axis approximately along the fiber direction for about a third of the crystallites. This is qualitatively what is expected from halite vectorial growth rates. The results of sections parallel to the fiber axis are not so clear but do show orientation effects.

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Mit 5 Abbildungen  相似文献   

Barents Sea upstream events impact the properties of Atlantic water inflow into the Arctic Ocean: Evidence from 2005 to 2006 downstream observations     

Igor A. Dmitrenko  Dorothea Bauch  Sergey A. Kirillov  Nikolay Koldunov  Peter J. Minnett  Vladimir V. Ivanov  Jens A. Hölemann  Leonid A. Timokhov 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(4):513-527

Inflow of Atlantic water (AW) from Fram Strait and the Barents Sea into the Arctic Ocean conditions the intermediate (100–1000 m) waters of the Arctic Ocean Eurasian margins. While over the Siberian margin the Fram Strait AW branch (FSBW) has exhibited continuous dramatic warming beginning in 2004, the tendency of the Barents Sea AW branch (BSBW) has remained poorly known. Here we document the contrary cooling tendency of the BSBW through the analysis of observational data collected from the icebreaker Kapitan Dranitsyn over the continental slope of the Eurasian Basin in 2005 and 2006. The CTD data from the R.V. Polarstern cruise in 1995 were used as a reference point for evaluating external atmospheric and sea-ice forcing and oxygen isotope analysis. Our data show that in 2006 the BSBW core was saltier (by ～0.037), cooler (by ～0.41 °C), denser (by ～0.04 kg/m³), deeper (by 150–200 m), and relatively better ventilated (by 7–8 μmol/kg of dissolved oxygen, or by 1.1–1.7% of saturation) compared with 2005. We hypothesize that the shift of the meridional wind from off-shore to on-shore direction during the BSBW translation through the Barents and northern Kara seas results in longer surface residence time for the BSBW sampled in 2006 compared with samples from 2005. The cooler, more saline, and better-ventilated BSBW sampled in 2006 may result from longer upstream translation through the Barents and northern Kara seas where the BSBW was modified by sea-ice formation and interaction with atmosphere. The data for stable oxygen isotopes from 1995 and 2006 reveals amplified brine modification of the BSBW core sampled downstream in 2006, which supports the assumption of an increased upstream residence time as indicated by wind patterns and dissolved oxygen values.  相似文献   

A data assimilation approach to discharge estimation from space     

Jeffrey Neal  Guy Schumann  Paul Bates  Wouter Buytaert  Patrick Matgen  Florian Pappenberger 《水文研究》2009,23(25):3641-3649

River discharge is currently monitored by a diminishing network of gauges, which provide a spatially incomplete picture of global discharges. This study assimilated water level information derived from a fused satellite Synthetic Aperture Radar (SAR) image and digital terrain model (DTM) with simulations from a coupled hydrological and hydrodynamic model to estimate discharge in an un‐gauged basin scenario. Assimilating water level measurements led to a 79% reduction in ensemble discharge uncertainty over the coupled hydrological hydrodynamic model alone. Measurement bias was evident, but the method still provided a means of improving estimates of discharge for high flows. The study demonstrates the potential of currently available synthetic aperture radar imagery to reduce discharge uncertainty in un‐gauged basins when combined with model simulations in a data assimilation framework, where sufficient topographic data are available. The work is timely because in the near future the launch of satellite radar missions will lead to a significant increase in the volume of data available for space‐borne discharge estimation. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Thermal and exhumation history of the central Rwenzori Mountains, Western Rift of the East African Rift System, Uganda   总被引：2，自引：1，他引：1  

F. U. Bauer  U. A. Glasmacher  U. Ring  A. Schumann  B. Nagudi 《International Journal of Earth Sciences》2010,99(7):1575-1597

The Rwenzori Mountains (Mtns) in west Uganda are the highest rift mountains on Earth and rise to more than 5,000 m. We apply low-temperature thermochronology (apatite fission-track (AFT) and apatite (U–Th–Sm)/He (AHe) analysis) for tracking the cooling history of the Rwenzori Mtns. Samples from the central and northern Rwenzoris reveal AFT ages between 195.0 (±8.4) Ma and 85.3 (±5.3) Ma, and AHe ages between 210.0 (±6.0) Ma to 24.9 (±0.5) Ma. Modelled time–temperature paths reflect a protracted cooling history with accelerated cooling in Permo-Triassic and Jurassic times, followed by a long period of constant and slow cooling, than succeeded by a renewed accelerated cooling in the Neogene. During the last 10 Ma, differentiated erosion and surface uplift affected the Rwenzori Mtns, with more pronounced uplift along the western flank. The final rock uplift of the Rwenzori Mtns that partly led to the formation of the recent topography must have been fast and in the near past (Pliocene to Pleistocene). Erosion could not compensate for the latest rock uplift, resulting in Oligocene to Miocene AHe ages.  相似文献   

Application of participatory principles to investigation of the natural world: An example from Chile     

Sarah Schumann 《Marine Policy》2010

Participatory research in environmental and natural resources-related fields is premised on many of the same notions that underlie participatory processes in decision making. This study examines one instance of participatory research to assess the extent to which the documented benefits of participatory decision-making hold up in the context of research. A survey of Chilean shell-fishers engaged in research with marine biologists assesses the relationships between four variables: fishers’ participation in research, fishers’ opinions of biologists, fishers’ trust in biologists, and fishers’ acquisition of knowledge from biologists. Results illuminate the multidimensionality of these variables and suggest that complex interrelationships between them make the benefits of participatory research more nuanced than those reported for participatory decision-making. For instance, participatory research may provide low benefits when participatory research outcomes differ little from those produced solely by scientists. In addition, high-cost scenarios may result when outcomes of participatory research are inferior to those produced solely by scientists. A third downside may result when participation leads participants to increase their deference to scientific knowledge, thereby defeating the corroborative purpose of their participation. A fourth effect may occur when increased trust by in scientists results from participation, decreasing participants’ perceived need to take part in research.  相似文献   

Geochemical and isotopic evidence of a groundwater source in the Corral Canyon meadow complex,central Nevada,USA     

Eliot A. Atekwana  Dorothea S. Richardson 《水文研究》2004,18(15):2801-2815

Major inorganic ions and stable carbon and oxygen isotopes in stream water, groundwater, groundwater seeps and springs were measured in the Corral Canyon meadow complex and watershed in the Toquima Mountains of central Nevada, USA. The purpose of the study was to determine whether stream water or groundwater was the source of water that supports vegetation in the meadow complex. Water samples from the watershed and meadow complex were mixed cation–HCO₃ type. Stream water sampled at different locations in the meadow complex showed variations in temperature, pH and specific conductance. The cation–anion proportions for stream water were similar to groundwater, groundwater seeps and runoff from the meadow complex. Stable oxygen isotope ratios for stream water (?17·1 to ?17·6‰ versus VSMOW) and groundwater and groundwater seeps in the meadow site (?17·0 to ?17·7‰ versus VSMOW) were similar, and consistent with a local meteoric origin. Dissolved inorganic carbon (DIC) and the δ ¹³C_DIC for stream water (?12·1 to ?15·0‰ versus VPDB) were different from that of groundwater from the meadow complex (?15·3 to ?19·9‰ versus VPDB), suggesting different carbon evolution pathways. However, a simple model based on cation–δ ¹³C_DIC suggests that stream water was being recharged by shallow groundwater, groundwater seeps and runoff from the meadow complex. This leads to the conclusion that the source of water that supports vegetation in the meadow complex was primarily groundwater. The results of this study suggest that multiple chemical and stable carbon isotope tracers are useful in determining the source of water that supports vegetation in meadow complexes in small alpine watersheds. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

A conceptually based stochastic point process model for daily stream‐flow generation     

Z. X. Xu  G. A. Schultz  A. Schumann 《水文研究》2002,16(15):3003-3017

Based on the stochastic and phenomenological aspects of hydrological processes, a conceptually based stochastic point process (SPP) model for daily stream‐flow generation is proposed in this paper. In which, storms are defined by a stochastic point process with marked values. All the random variables defining the process are assumed to be mutually independent, which constitutes a compound Poisson point process. The direct surface runoff is regarded as occurring from storage in a cascade of surface linear reservoirs and is responsible for the short‐term variation of the daily stream flows. The baseflow component is considered as coming from subsurface/groundwater storage and is responsible for the long‐term persistence of the storm time‐series. This type of model is proposed as a more realistic model of daily stream flow than models based on pure stochastic processes. Studies on the instantaneous unit hydrograph and the mechanism of baseflow could thereby provide some parameters for this model. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献