The annual cycle and long-term trend of the methane total column in the atmosphere over the Petergof station (St. Petersburg State University) are analyzed on the basis of data obtained from Fourier-transform infrared spectrometry and EMAC-model calculations. The amplitude of the annual cycle of the total column of CH4 amounts to 2.1 and 1.5% according to experimental and model data, respectively. For the atmospheric column-averaged mole fraction of CH4, the amplitude of its annual cycle is smaller than that for its total column and amounts to 1.1 and 0.6% according to experimental and model data, respectively. The results of local continuous measurements of surface CH4 concentrations showed that, in 2013, the atmospheric column-averaged mole fractions of CH4 and the amplitudes of diurnal variations in its local concentration were characterized by the same dynamics of seasonal variations. An analysis made on the basis of simulation results showed that atmospheric conditions (under which Fourier-transform IR measurements were performed) could increase the amplitude of the annual cycle of the total column of CH4 2.5 times when compared to the true one. The results of Fourier-transform IR measurements and EMAC-model calculations showed that, during 2009–2012, the atmospheric concentration of CH4 increased at a rate of ~0.2% per year. If measurement data obtained in 2013 are added, this rate decreases to ~0.13% per year.
Annual cycle and long-term trend of the methane total column in the atmosphere over the St. Petersburg region
Makarova, M.V., Kirner, O., Timofeev, Yu.M., Poberovskii, A.V., Imkhasin, Kh.Kh., Osipov, S.I., and Makarov, B.K.
Izvestiya, Atmospheric and Oceanic Physics, 51, 4, 431-438, doi: 10.1134/S0001433815040088