Figure 2

Summary of MII optical properties observations of Etna’s plume during C2 campaign (18–22/07/2016, a): AE (proportional to the size of the markers), \(\beta\) (white–grey–black shade of the markers), UV AOD (height of the column during plume traverse). The different experiments are also individuated in (a): plume half-traverse and the two plume transects scans (TS1 and TS2). The location of the LiDAR station is indicated with a blue cross. The locations of FLAME stations are indicated with red triangles. The background map is generated with Google Maps (https://www.google.com/maps/, Map data \(\copyright 2020\) Google). AE as a function of distance (b) and of \(\beta\) coefficient (c), for MIIOM measurements collected during C2 campaign (in red) and for MIISP measurements collected during C3 campaign (blue). Individual points and error bars are associated to average values and variability for observations sessions at fixed locations (see Table 1). Regression lines are also reported (red and blue dashed lines) with their Pearson \(\hbox {R}^2\) coefficients.