Time and space variations of tropospheric carbon dioxide over Japan

Aircraft measurements of atmospheric CO₂ concentration over Japan, initiated in January 1979, have been continued to the present. The average seasonal variation of atmospheric CO₂ showed maximum concentration early in April and early in May, and minimum concentration in mid‐August and mid‐September for the lower‐most and the upper‐most layers of the troposphere, respectively. The peak‐to‐peak amplitudes of the seasonal variation were 14.5, 9.0 and 7.8 ppmv for the lower, middle and upper tropospheres, respectively. The average rate of annual increase of the CO₂ concentration over the last 6 years was about 1.3 ppmv yr⁻¹ with considerable variation with time. The vertical profile of the annual mean value of the CO₂ concentration was almost the same from year to year; the CO₂ concentration decreased gradually with height and the concentration difference between the lowest and highest layers of the troposphere was about 2 ppmv. 1987 Blackwell Munksgaard