TRENDS OF TROPOSPHERIC CO, N2O AND CH4 AS OBSERVED AT CAPE POINT, SOUTH-AFRICA

The results of CO, CH4 and N2O measurements performed over several years at the station Cape Point (34°21′S, 18dg29′E), South Africa, are presented. The analytical technique and data filtering procedure are described. The results indicate seasonal variations of the CO and CH4 mixing ratios with maximum values around October and minimum values in February/March. The patterns and the amplitudes of the seasonal variations of both gases compare suprisingly well, indicating interrelations between the source-sink and/or transport mechanisms of CH4 and CO in the Southern Hemisphere. CO measurements performed over a period of 9 years do not show any significant trend of the mean annual CO mixing ratios while the N2O mixing ratios increase at a rate of 0.2% per year for the observation period from 1983 to 1987. The data obtained for CH4 between 1983 and 1987 yield an increase rate of 0.7% per year indicating a reduction of the CH4 increase in the Southern Hemisphere during recent years. © 1990.