Estimation of Particle Mass Concentration from Lidar Measurement

Vertical distribution of particle mass (PM) concentrations are estimated from 10 year (2006-2015) elastic-backscatter lidar and sky radiometer data, and from ground-level PM (diameter ≤ 10 μm) mass concentrations measured in Seoul, Korea. We firstly categorize aerosol-cloud and aerosol types (clean continental, dust, and polluted continental/urban pollution aerosols), and then generate vertically resolved distributions of aerosol extinction coefficient, as well as, aerosol mass concentration. Extinction-to-backscatter ratio (so called, lidar ratio) and aerosol mass extinction efficiency were determined from co-located sky radiometer and PM10 mass concentration measurements from June 2006 to December 2015. The mean lidar ratio and mass extinction efficiency for the entire 10 year study period were 63.31 sr and 3.36 m2 g-1 (1.39 m2 g-1 for dust), respectively. The lidar ratio did not vary significantly with the Ångström exponent (less than ± 10%). However, the mass extinction efficiency decreases to 1.82 ± 1.67 m2 g-1 when Ångström exponent is less than 0.5. This result implies that the PM mass concentration from lidar measurements can be underestimated for dust events. The lidar-derived aerosol mass concentrations well match with PM10 mass concentrations. Mean bias difference between PM10 and lidar-derived aerosol mass concentrations estimated from the same study period is about 3 μg m-3. Seasonal variation of the PM mass concentration estimated from lidar measurements for the boundary layer, was quite different from ground-level PM10 measurements. This can be attributable to an inhomogeneous vertical distribution of aerosol in the boundary layer.