Figure 3. Example of far field scan at Pisciarelli.

(a) Range measurements versus scan angle (heading). The ranges were measured using a range finder LIDAR (Methods). They defined the path length. (b) Grand ratio (GR) versus heading. (c) Total path averaged CO₂ concentration. Also shown is the measurement precision (1 SD) in grey. (d) In-plume CO₂ concentrations. They were derived from data in c) using Equation 4 (Methods). The numbered triangles depict the values and ranges as well as lateral position uncertainties of the in situ measurements (Fig. 1c). Note that these have been acquired ~20h earlier. Thus, they serve as approximate reference only. Moreover, concentrations in d) from the CO₂DIAL represent path averages with contributions from across the plume, while the in situ values show concentrations measured at a single point in the plume.