Signal contribution to the RPK site during two distinct periods, shown with emission time series from an influential nearby point source. Maps of average gridded contribution to prior and true CO₂ signals at the RPK site are shown for September 8–16 (left column) and September 19–22, 27–29 (right column). A prominent point source is identified in the circled grid cell and the time series of emissions at the grid cell are shown below for the month of September 2015. Respective time periods are shown in the emission maps by dotted boxes in red (September 8–16) and violet (September 19–22, 27–29). DOI: https://doi.org/10.1525/elementa.375.f10