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

Abstract

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 αref 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 αref 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, αref obtained through the multi-section method reflects typical atmospheric aerosols unaffected by emissions and noise. When comparing αref to the PM2.5 mass concentrations at national monitoring stations near the measurement area, a significant correlation with an r2 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 PM2.5 concentrations.