## 3 Results
### RCS, Extinction, Backscatter Coefficients, and Angstrom Exponent Profiles  
In the following, we report the logarithm of the RCS, the derived extinction and backscatter coefficients, and the LIDAR ratio and Angstrom exponent profiles for the more interesting data sets D-III, D-IV. During the calima event (D-III), the Raman channel readout was unfortunately not yet sufficiently calibrated or reliable, and it has been omitted in this study. Figure 25  
Figure 23: Two-dimensional RHI diagrams are obtained using barycentric interpolation for the calculation of a weighted logarithm of range-square corrected LIDAR return values for pixels \(w(x,y)\) between LIDAR profiles at two successive zenith angles, highlighted in blue. Values \(v(x_{1},y_{1})\) and \(v(x_{2},y_{2})\) from the two profiles that are closest to \(w(x,y)\) are used and weighted by their respective distances from the interpolated pixel. Decreasing the zenith angle step increases the spatial resolution of the image. Figure 24: Spatial distribution of clouds and aerosol loading above the ORM (RHI diagrams). **Left**: The night of 25 August 2021 (D-III) with presence of calima. The plot is based on five 90 s long measurements in the 355 nm return channel at different zenith angles ranging from 0\({}^{\circ}\) to 60\({}^{\circ}\) in steps that correspond to regular increases from air mass of 1 to air mass of \(\sim\)2. **Right**: The night of 22 September 2021 (D-IV) during the volcano event. The figure is based on seven 200 s long measurements in the 355 nm return channel at different zenith angles ranging from 0\({}^{\circ}\) to 30\({}^{\circ}\), taken in steps of 5\({}^{\circ}\). A barycentric interpolation was used to fill the gaps. The volcanic ash layer is clearly visible 1500 m above the observatory (approximately 3700 m a.s.l.). therefore shows only the two elastic lines to highlight the pBRL's capacity to retrieve Angstrom exponents. We have assumed typical LIDAR ratios of around 50 sr [72] for this event and found Angstrom exponents of 1.82 \(\pm\) 0.13, which implies scattering on large, irregularly shaped particles, such as mineral dust [72; 73; 74]. Furthermore, we found that the layer is structured and contains a lower part showing a slightly higher Angstrom exponent of \(\sim\)2.6. Toward the upper end of the higher layer, the Angstrom exponent rises to values consistent with accumulation-mode particle sizes. Note also the slightly higher Angstrom exponent retrieved for the lower layer centred at 450 m, and the significantly increasing Angstrom exponent at the upper edge of the second layer, around 800 m.  
Especially interesting is the case on 25 August 2021, where a zenith scan (Figure 24) revealed that the dust was not stratified on the top of the island, consistent with the findings of [9]. The case of the volcano event (D-IV) has been selected to highlight the pBRL's capacity to derive extinction and backscatter coefficients as well as LIDAR ratio profiles. Figure 26 highlights the capability of the two elastic lines and a repaired Raman line. The retrieved extinction profiles show two peaks: a lower one around 1.5 km altitude, where the volcano dust debris is blown over the observatory, and another structured layer above 2.2 km. Both layers are detected in both elastic channels and the Raman channel, though the latter has a poorer range resolution in the upper layer. Analysis of three channels separately reveals excellent agreement of retrieved extinction profiles (if the different range resolutions for the upper layer are taken into account). From the extinction and backscatter profile, we obtain a LIDAR ratio of (103 \(\pm\) 12) sr at 355 nm and (88 \(\pm\) 14) sr at 532 nm for the volcano debris layer. The LIDAR ratio profile has a range resolution of about 50 m in this case. Note that the less accurate iterative Klett inversion has provided 83 sr for the 355 nm line, but only 26 sr in the green line, strengthening the shortcomings of an analysis based on elastic channels only.