Time variability of the total methane content in the atmosphere over the vicinity of St. Petersburg |
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Authors: | M V Makarova A V Poberovskii K N Visheratin A V Polyakov |
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Institution: | 1.St. Petersburg State University,Petrodvorets, St. Petersburg,Russia;2.Taifun Research and Production Association,Obninsk, Kaluzhskaya oblast,Russia |
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Abstract: | The results of measuring the methane content in the entire atmospheric thickness over the St. Petersburg region are given
for 1991–2007. It is shown that, within this period, the mean annual cycle of the total methane content is characterized by
its maximum values in December–January and its minimum values in June–August when the annual-cycle amplitude amounts to ∼3.6%.
In this case, the annual variations in the total methane content may differ significantly from the mean annual cycle obtained
in some years. A statistically significant linear trend of the total CH4 content has not been revealed for 1991–2007. The obtained values of the linear-trend index have opposite signs in the winter
and summer months (positive for January 0.6 ± 0.2%/year and February 0.4 ± 0.2%/year and negative for July 0.3 ± 0.2%/year
and August 0.2 ± 0.1%/year). This fact suggests the tendency for an increase in the amplitude of the annual cycle of the total
CH4 content. The results of a spectral analysis of a series of data on the total CH4 content show that, for 1991–2007, the following harmonics are pronounced with a confidence of 95%: 12 months (annual harmonic),
32 months (quasi-biennial oscillations), and 55 months (4.5 years), which are also pronounced in the series of meteorological
parameters and total ozone content. |
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