## 5 Conclusions  
The present work has demonstrated the feasibility of our self-designed short-range elastic backscatter micro-lidar to provide relevant properties of aerosol plumes, including radiative and microphysical properties. An indoor measurement campaign was carried out to assess the performances of the micro-lidar under controlled environment conditions. This campaign allowed us to monitor the dynamics of aerosol plumes and to retrieve quantitative micro-lidar products, including aerosol backscatter and number concentration profiles as a result of a rigorous calibration and a dedicated inverse method without any boundary condition. In a nutshell, the following highlights can be drawn from our in-door measurement campaign using the Colibri micro-lidar:  
1. Short-range elastic backscatter lidar measurements were proved to measure backscattering from aerosol plumes in the short-range (within the first tens of meters) with a high range-resolution (<10 cm) and a high-temporal-resolution (1 ms);
2. The inversion of micro-lidar signals was made possible using a forward inverse method without boundary conditions;
3. Aerosol backscatter and number concentration profiles could be retrieved using lidar-relevant parameters derived from light-scattering models and ancillary in-situ instruments. The Colibri micro-lidar fills technological gaps (i.e., high range-resolution, short-range) that current elastic lidar systems have not yet covered. Such high-resolution could enable lidar measurements of small aerosol plumes or rapidly changing aerosol events. For instance, it could enable the study of radiative and microphysical properties of aerosols associated with complex atmospheric processes such as new particle formation (i.e., nucleation process) and aerosol dynamics inside the atmospheric boundary layer, and also for the characterization of the emitting sources in industrial and aeronautics sectors. These aerosol lidar products are currently necessary for different atmospheric research and industrial fields. Furthermore, it is \begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{3}{l}{**Averaged Aerosol Number Concentration**} \\ \hline
**Instrument** & **Value** & **Units** \\ \hline Colibri & 3990 \(\pm\) 130 & part cm\({}^{-3}\) \\ Fidas 200 & 4055 \(\pm\) 400 & part cm\({}^{-3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Range and 60 s time-averaged aerosol number concentration \(\langle N_{p}\rangle\) derived from the Colibri micro-lidar and aerosol number concentration from Fidas 200 optical counter. worth noting that the aerosol plume was never in contact with our system, which supports the potential use of this system for standoff sensing of particulate matter such as hazardous industrial plumes or aerosolized bioagent for instance. For transferring the Colibri micro-lidar from indoor tunnel measurements to outdoor field campaigns, the current prototype should undergo a series of adjustments, including an adaptation of interference filter and spatial filter to improve the rejection of ambient background light and optimize the signal-to-noise ratio. Moreover, a challenge in aerosol lidar has been for many years to rigorously account for the validity of the single-scattering approximation. To improve the quality of micro-lidar retrievals for dense aerosol plumes, the relative contribution of multiple-scattering should be evaluated in the future, and additionally, the instrument is planned to be extended to multi-wavelength operation in order to retrieve high-level products such as high spatio-temporal Angstrom Exponent and color ratio products in order to go further at investigating complex topics such as aerosol-cloud interaction (i.e., inside the Atmospheric Boundary Layer Cirrus clouds and fog formation near to the surface), which are essentials for the Earth's radiative balance calculations and atmospheric modeling. Additionally, our results suggest the implementation of new aerosol field campaigns for having a long-term database of aerosol properties.