Temporal and spatial variations of upper tropospheric and lower stratospheric carbon dioxide

Systematic collection of air samples was made using commercial jet airliners between Tokyo, Japan and Anchorage, Alaska and between Tokyo and Sydney, Australia in 1984 and 1985. The amplitude of the seasonal CO₂ cycle in the upper troposphere was found to be largest in high latitudes of the northern hemisphere but decreased and lagged in phase as the equator was approached. The cycle was still clearly observable in the southern hemisphere, due to southward transport of the northern hemispheric air through the upper troposphere by a monsoon circulation. The yearly mean value of the upper tropospheric CO₂ was high in the equatorial region and decreased poleward. The seasonal cycle of the lower stratospheric CO₂ in northern high latitudes showed a minimum concentration early in May and a maximum concentration early in September, with a peak-to-peak amplitude of 2.2 ppmv. Yearly mean CO₂ concentrations were lower by 1.4-2.2 ppmv than those in the upper troposphere. The difference in yearly mean CO₂ concentrations between 1984 and 1985 was about 1.1 ppmv at all locations covered by this measurement.