Anthropogenic CO${}_2$ emission estimates in the Tokyo metropolitan area from ground-based CO${}_2$ column observations

Urban areas are responsible for more than 40 % of global energy-related carbon dioxide (CO${}_2$) emis-
sions. The Tokyo metropolitan area (TMA), Japan, one of the most populated regions in the world, includes
various emission sources, such as thermal power plants, automobile traffic, and residential facilities. In order to
infer a top–down emission estimate, we conducted an intensive field campaign in the TMA from February to
April 2016 to measure column-averaged dry-air mole fractions of CO${}_2$ (XCO${}_2$) with three ground-based Fourier
transform spectrometers (one IFS 125HR and two EM27/SUN spectrometers). At two urban sites (Saitama and
Sodegaura), measured XCO${}_2$ values were generally larger than those at a rural site (Tsukuba) by up to 9.5 ppm,
and average diurnal variations increased toward evening.