The distribution characteristics of atmospheric methane over Lake Baikal, Siberia by SCIAMACHY remotely sensed data

Freshwater environments contribute more than 20% of total CH₄ flux to the atmosphere, and the lakes are one of the major natural sources of atmospheric CH₄, mainly in boreal lakes. So, we present and analyze the temporal and spatial variations of CH₄ VMRs over Lake Baikal, the only freshwater body, the unique large and high latitude lake, based on the retrieved monthly CH₄ data from SCIAMACHY spectra. The result showed that monthly CH₄ concentrations in atmosphere extended between 1744.780ppb and 1818.495ppb. The value in March was a relative higher value, and then increased from April to August. After this growing, the CH₄ concentration decreased to September. But, there was an increased trend in October. Overall, the temporal pattern liked the ocean pattern during the growing season, and was in line with permafrost in other time. Moreover, the spatial distribution of CH₄ VMRs showed that the values were higher in North Lake Baikal, followed by South, Center. The crucial controlling factor for the seasonal variation of CH₄ concentration and spatial difference was both temperature, the amount of organic matter in the sediment and stability of hydrate. This exerted a direct influence on diatom and CH₄ source plus (hydrate). Furthermore, the monthly CH₄ concentrations by air transport were few for the size of basin over Lake Baikal and mountain barriers. So the source over Lake Baikal was itself. Based the average annual mean (8 months) atmospheric CH₄ concentration and the area of the Lake Baikal (31494Km²), the annual CH₄ flux (at all atmospheric altitude levels) was roughly estimated to be 40.03Mg yr (-1) (mean) during the period (March-October, 2003).