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- ItemGlobal annual methane emission rate derived from its current atmospheric mixing ratio and estimated lifetime(Göttingen : Copernicus, 2014) Sonnemann, G.R.; Grygalashvyly, M.We use the estimated lifetime of methane (CH4), the current methane concentration, and its annual growth rate to calculate the global methane emission rate. The upper and lower limits of the annual global methane emission rate, depending on loss of CH4 into the stratosphere and methane consuming bacteria, amounts to 648.0 Mt a-1 and 608.0 Mt a-1. These values are in reasonable agreement with satellite and with much more accurate in situ measurements of methane. We estimate a mean tropospheric and mass-weighted temperature related to the reaction rate and employ a mean OH-concentration to calculate a mean methane lifetime. The estimated atmospheric lifetime of methane amounts to 8.28 years and 8.84 years, respectively. In order to improve the analysis a realistic 3D-calculations should be performed.
- ItemUpper stratospheric ozone decrease events due to a positive feedback between ozone and the ozone dissociation rate(Göttingen : Copernicus, 2009) Sonnemann, G.R.; Hartogh, P.Ozone measurements taken with a ground based microwave instrument at Lindau (51.66° N, 10.13° E) over some years showed strong ozone decrease events within the stratopause region, particularly during the winter half-year. These events are characterized by a marked drop of the ozone mixing ratio from two to three ppmv to less than half a ppmv in extreme cases. Simultaneous water vapor measurements at the same place, also carried out by a microwave instrument, showed a strong increase of its mixing ratio and the temperature was also enhanced during these episodes. The theoretical analysis brought evidence that these events result from a positive feedback in the complex radiatively-chemical system between the ozone column density and the ozone dissociation rate.