ATMOSPHERIC METHANE CONCENTRATION BETWEEN TOKYO AND SYOWA STATION, ANTARCTICA

Air samples were collected on board at intervals of about 5-degrees in latitude between Tokyo and Syowa Station late in 1987 and 1988, and methane was measured by a GC-FID method. South of the intertropical convergence zone (ITCZ), mixing ratios were almost constant through Syowa Station. Their mean values and standard deviations were 1.578 and 0.008 ppm in 1984(2)), 1.611 and 0.012 ppm in 1987, and 1.628 and 0.008 ppm in 1988. The average increase rate of these mean values was 0.013 ppm/y from 1984 to 1988. On the north of ITCZ, mixing ratios in 1987 were higher than those of 1988 against the increasing trend observed south of ITCZ. This can be explained by the meterological conditions when air samples were collected.