Concentration of atmospheric carbon dioxide at 500 and 700 millibars

Abstract

The distribution of atmospheric carbon dioxide over the North Pacific and Arctic oceans has been determined as a function of season from 1008 samples of air collected at the 500- and 700-mb pressure surfaces by Weather Reconnaissance flights of the U.S. Air Force over a period of 4 years beginning in 1958. The concentration (mixing ratio) of CO2 oscillates seasonally. The amplitude increases and the phase advances from south to north. Variations with altitude are slight. Typical monthly mean values referred to a 1960 datum are: south of 20°N, maximum of 316 ppm in June, minimum of 311 ppm in October; north of 70°N, maximum of 317 ppm in May, minimum of 308 ppm in August. Significant horizontal variations in CO2 concentration are observed on the scale of weather patterns during the summer, when photosynthesis by land plants produces an intense sink for CO2. During other seasons the concentration is uniform over great distances.