Observed time-averaged afternoon CO₂ dry mole fraction above background (Site 01). The averaging period is 1 January – 30 April 2013. The site number is shown in the upper right corner of each plot and the average observed CO₂ above background (in ppm) in the upper left corner. The full y-axis scale for the plots is 4.5 ppm CO₂. Red filled circles indicate the locations of the sites, with the background Site 01 indicated by a red star. Time frame is chosen to minimize biogenic signals and maximize the number of sites with available data. Sites with less than 75% data availability during the selected time period are excluded. DOI: https://doi.org/10.1525/elementa.127.f8