Trends in methane and sulfur hexafluoride at a tropical coastal site, Thumba (8.6^oN, 77.^oE), in India [An article from: Atmospheric Environment]

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Description:
Measurements of methane (CH"4) and sulfur hexafluoride (SF"6) have been made using gas chromatographic technique at a coastal site, Thumba (8.6^oN, 77^oE), India from the flask air samples collected during 1996-2000. The growth rates of CH"4 and SF"6 are observed to be 30 and 0.25pptvyr^-^1 respectively. The growth rate of CH"4 at Thumba is found to be much higher than its average growth rate of about 7ppbvyr^-^1 at other tropical monitoring sites. The observed growth rate of SF"6 at Thumba is similar to that found at other tropical stations. Seasonal amplitudes in CH"4 and SF"6 are higher at Thumba when compared to the other sites. The large growth rate of CH"4 at Thumba could be attributed to the increase in regional sources, and the greater seasonal amplitude is shown to be caused by the change in dynamical structure from Northern Hemisphere summer to winter.