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  • 1
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: Online-Ressource (23 S., 201 KB) , graph. Darst.
    Language: German , English
    Note: Förderkennzeichen BMBF 50FE0017 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Auch als gedr. Ausg. vorhanden , Systemvoraussetzungen: Acrobat reader. , Bericht überw. dt., teilw. engl.
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  • 2
    Publication Date: 2023-07-20
    Description: Volatiles released from magma can form bubbles and leave the magma body to eventually mix with atmospheric air. The composition of those volatiles, as derived from measurements made after their emission, is used to draw conclusions on processes in the Earth's interior or their influences on Earth's atmosphere. So far, the discussion of the influence of high‐temperature mixing with atmospheric air (in particular oxygen) on the measured volcanic gas composition is almost exclusively based on thermodynamic equilibrium (TE) considerations. By modeling the combined effects of C‐H‐O‐S reaction kinetics, turbulent mixing, and associated cooling during the first seconds after magmatic gas release into the atmosphere we show that the resulting gas compositions generally do not represent TE states, with individual species (e.g., CO, H2, H2S, OCS, SO3, HO2, H2O2) deviating by orders of magnitude from equilibrium levels. Besides revealing the chemical details of high‐temperature emission processes, our results question common interpretations of volcanic gas studies, particularly affecting the present understanding of auto‐catalytic conversion of volcanic halogen species in the atmosphere and redox state determination from volcanic plume gas measurements.
    Description: Plain Language Summary: A major fraction of magmatic gas emissions are released into the atmosphere from open vents. The emission processes are characterized by fast turbulent mixing with atmospheric air (within seconds) and associated rapid cooling. Hardly anything is known about the chemical kinetics within this brief mixing and cooling period. We simulate the chemical kinetics during the first seconds of hot magmatic gases in the atmosphere and find severe deviation to common interpretations and central thermodynamic equilibrium assumptions prevailing in volcanic gas geochemistry.
    Description: Key Points: We model the chemical kinetics of high‐temperature volcanic gas emissions within the first seconds of mixing with atmospheric air. We identify key chemical processes within the magma‐atmosphere interface and quantify influences on the volcanic plume composition. Our results question common assumptions prevailing in volcanic gas geochemistry and refine interpretations of gas emissions from open vents.
    Description: German Research Foundation
    Keywords: ddc:551.9 ; volcanic gas emissions ; kinetic chemistry modeling ; atmospheric chemistry ; magmatic redox states ; reactive halogen chemistry
    Language: English
    Type: doc-type:article
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 285 (1980), S. 312-314 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Nitrous acid was detected and monitored using the long path differential UV absorption technique described by Platt et al6. The optical system in the present experiments used a 0.3m McPherson spectrograph with a 600 grooves mm-1 grating blazed at 500 nm (giving a dispersion of 5.3nm per mm). A ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 395 (1998), S. 486-490 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Reactive bromine species contribute significantly to the destruction of ozone in the polar stratosphere. Reactive halogen compounds can have a strong effect not only on the chemistry of the stratosphere but also on that of the underlying troposphere. For example, severe ozone depletion events ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 153 (1994), S. 287-306 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the influence of the finite extent of the computational domain and of specific boundary conditions on a theoretical model for solar eruptive processes originally proposed by Zwingmann (1987). In this model, the slow pre-onset time evolution of arcade-like solar coronal magnetic field structures is described by quasi-static equilibrium sequences. The magnetic field is represented by Euler potentials which allow for a realistic description of the photospheric boundary conditions, because the pressure and the magnetic footpoint displacement can be prescribed separately. We use an improved numerical method suitable for computing equilibrium sequences, allowing for larger domains and higher resolution than used in the previous work. With this method, we are able to show that, in contradiction to a supposition made by Zwingmann (1987), the results of the computations do strongly depend on the size of the computing domain. This has consequences for a possible physical interpretation of the model. We furthermore show that with the boundary conditions used in this model a shearing motion of the magnetic footpoints inevitably leads to the formation of singular current layers at the separatrix between field lines cutting the upper boundary (open field lines) and field lines which are only connected with the photosphere (closed field lines).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 348 (1990), S. 147-149 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The chemical processes we discuss here are initiated by reaction of NO2 with ozone to form NO3 radicals NO2 + O3 -〉 NO3 + O2 (1) Depending on the trace-gas composition of the air mass, several reactions can generate peroxy radicals (see Table 1). For instance, they are generated by the ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillian Magazines Ltd.
    Nature 423 (2003), S. 273-276 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The emission of volcanic gases usually precedes eruptive activity, providing both a warning signal and an indication of the nature of the lava soon to be erupted. Additionally, volcanic emissions are a significant source of gases and particles to the atmosphere, influencing tropospheric and ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Annales geophysicae 17 (1999), S. 1457-1462 
    ISSN: 0992-7689
    Keywords: Atmospheric composition and structure (aerosols and particles, cloud physics and chemistry) ; Meteorology and atmospheric dynamics (mesoscale meteorology)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Polar stratospheric clouds (PSCs) are often observed in the Kiruna region in northern Sweden, east of the Scandinavian mountain range, during wintertime. PSC occurrence can be detected by ground-based optical instruments. Most of these require clear tropospheric weather. By applying the zenith-sky colour index technique, which works under most weather conditions, the data availability can be extended. The observations suggest that PSC events, especially of type II (water PSCs) may indeed more common than predicted by synoptic models, which is expected because of the frequent presence of mountain-induced leewaves. However, it will be of importance to increase the density of independent observations.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of atmospheric chemistry 15 (1992), S. 203-214 
    ISSN: 1573-0662
    Keywords: Maritime troposphere ; trace gas measurements ; oxidant formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A comprehensive set of trace gas concentrations and meteorological parameters were measured simultaneously during a cruise of the research vessel Polarstern from Bremerhaven (54° N, 8° E) to Rio Grande (32° S, 52° W) during the period from 15 September to 9 October 1988. This paper describes the general features of the cruise and summarizes the measurements made, the techniques employed, and the placement of the instruments on board the ship. The synoptic data base is used to characterize the nature and possible origins of the air masses encountered during the cruise and to draw some general conclusions from the measurements.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-0662
    Keywords: Photolysis frequency ; J(O1D), O3, H2O ; OH production rate ; meridional cross-section ; marine atmosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The latitudinal variation of the photolysis frequency of ozone to O(1D) atoms, J(O1D), was measured using a filter radiometer during the cruise ANT VII/1 of the research vessel Polarstern in September/October 1988. The J(O1D) noon values exhibited a maximum of 3.6×10-5 s-1 (2π sr) at the equator and decreased strongly towards higher latitudes. J(O1D) reached highest values for clean marine background air with low aerosol load and almost cloudless sky. The J(O1D) data, measured under these conditions and a temperature of 295 K, can be expressed by: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOsaiaacI% cacaqGpbWaaWbaaSqabeaaiiaacqWF8baFaaGccaqGebGaaeykaiaa% bccacqWF9aqpcaqGGaGaaeyzaiaabIhacaqGWbGaaeiiaiaabUhacq% GHsislcaaI4aGaaiOlaiaaicdacaaIYaGaeyOeI0IaaGioaiaac6ca% caaI4aGaaiiEaiaaigdacaaIWaWaaWbaaSqabeaacqGHsislcaaIZa% aaaOGaaeiiaiaabIhacaqGGaGaam4uaiabgUcaRiaaiodacaGGUaGa% aGinaiaacIhacaaIXaGaaGimamaaCaaaleqabaGaeyOeI0IaaGOnaa% aakiaadofadaahaaWcbeqaaiaaikdaaaGccaGG9bGaaeikaiaaboha% daahaaWcbeqaaiabgkHiTiaaigdaaaGccaGGPaaaaa!5EE9!\[J({\text{O}}^| {\text{D) }} = {\text{ exp \{ }} - 8.02 - 8.8x10^{ - 3} {\text{ x }}S + 3.4x10^{ - 6} S^2 \} {\text{(s}}^{ - 1} )\] where S represents the product of the overhead ozone column (DU) and the secant of the solar zenith angle. The meridional profile of the primary OH radical production rate P(OH) was calculated from the J(O1D) measurements and simultaneously recorded O3 and H2O mixing ratios. While the latitudinal distribution of J(O1D) and water vapour was nearly symmetric to the equator, high tropospheric ozone levels up to 40 ppb were observed in the Southern Hemisphere, SH, resulting in higher P(OH) in the SH.
    Type of Medium: Electronic Resource
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