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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Pure and applied geophysics 116 (1978), S. 452-464 
    ISSN: 1420-9136
    Schlagwort(e): Trace gases ; Atmosphere ; Sources and Sinks ; Methane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract In 1972 average mixing ratio of methane in the troposphere was 1.41 ppm and 1.3 ppmv for the northern and southern hemisphere, respectively, which corresponds to a total amount of 4×1015 g of CH4 present in the atmosphere. Most is of recent biologic origin.14C analyses show that no more than 20 percent is released by fossil sources. The various ecosystems producing CH4 are discussed and the total annual production is estimated to lie between 5.5×1014 g/yr and 11×1014 g/yr. The corresponding turnover times for atmospheric CH4 range from 4 to 7 yrs. The destruction of CH4 takes place mainly in the troposphere, most probably through the reaction of CH4 + OH ↠ CH3 + H2O. About 10 percent of the CH4 is destroyed in the stratosphere. The CH4 cycle contributes on the order of 1 percent to the atmospheric carbon cycle.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-0662
    Schlagwort(e): OH intercomparison ; laser absorption spectroscopy ; DOAS ; laser induced fluorescence ; LIF ; troposphere
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract In-situ OH measurements by laser-induced fluorescence (LIF) spectroscopy and folded long-path differential optical absorption spectroscopy (DOAS) were carried out in a rural environment in North-East Germany as part of the field experiment POPCORN in August 1994. The large set of OH data obtained allowed an intercomparison of both techniques based on relative diurnal profiles and simultaneously measured absolute concentrations. Most of the time the two OH instruments encountered the same air and agreed well in the measured relative diurnal variations. Only on a few occasions the measurements significantly disagreed due to a perturbation of the DOAS measurements by a local OH source in the north-western wind sector. Excluding data from this wind direction, the statistical analysis of 137 data pairs yields a correlation coefficient of r = 0.90 and a weighted linear fit with a slope of 1.09 ± 0.12. The correlations are carefully analyzed. The comparison of both instruments is discussed in the light of newly published effective absorption cross-sections for H2O and O2 that affect the calibration of LIF.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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