Consumption of atmospheric O<sub>2</sub> in an Urban Area of Tokyo, Japan derived from continuous observations of O<sub>2</sub> and CO<sub>2</sub> concentrations and CO<sub>2</sub> flux
Abstract. In order to estimate the atmospheric O2 consumption in a megacity, continuous observations of atmospheric O2 and CO2 concentrations and of CO2 flux have been carried out simultaneously at the Yoyogi (YYG) site in middle of Tokyo, Japan since March 2016. An average O2 : CO2 exchange ratio for net turbulent O2 and CO2 fluxes (ORF) between the urban area and the overlying atmosphere was obtained based on an aerodynamic method using the observed O2 and CO2 concentrations. The yearly mean ORF was found to be 1.62, falling within the range of the average OR values of liquid and gas fuels. Seasonally different diurnal ORF cycles at YYG indicated that the consumption of gas fuels was larger in the winter than that in the summer, especially in the morning and late in the evening. By using the ORF and CO2 flux values, the annual mean O2 consumption rate was estimated to be −16.3 μmol m−2 s−1, which is more than 350 times larger than the global mean atmospheric O2 consumption rate (about −4 μmol yr−1), implying that our life in a megacity is far from sustainable from a viewpoint of the conservation of atmospheric O2.