Multi-section reference value for the analysis of horizontally scanning aerosol lidar observations

The quantitative analysis of measurements with horizontally scanning aerosol lidar instruments faces two major challenges: the background correction can be affected by abnormal signal peaks, and the choice of a reference extinction coefficient alpha ref is complicated if aerosols are ubiquitous in the sampled volume. Here, we present the newly developed multi-section method for the stable solution of extinction coefficient retrievals from horizontally scanning lidar measurements. The algorithm removes irregular peaks related to signal noise based on an experimentally derived fitting model. A representative value for alpha ref is inferred from converging retrievals along different scan axes and over multiple scans of 10 to 15 min under the assumption that they are only related to ambient aerosols without distinct emission sources. Consequently, alpha ref obtained through the multi-section method reflects typical atmospheric aerosols unaffected by emissions and noise. When comparing alpha ref to the PM 2.5 mass concentrations at national monitoring stations near the measurement area, a significant correlation with an r 2 value exceeding 0.74 was observed. The presented case studies show that the new method allows for the retrieval and visualization of spatio-temporal aerosol distributions and subsequent products such as PM 2.5 concentrations.