Retrieval of aerosol liquid water content from high spectral resolution lidar

Aerosol liquid water content (ALWC) has significant effects on aerosol optical properties, radiative forcing, and the development of severe pollution events. In this study, the vertical distribution and temporal evolution of ALWC were determined through linear particle depolarization measured by a high spectral resolution lidar (HSRL) from December 9 to 12, 2020. Near-surface ALWC datasets retrieved by HSRL were validated by measurements from a three-wavelength humidified nephelometer. The ALWC datasets derived by two methods were highly correlated (R = 0.94, N = 192), illustrating the feasibility of retrieving the ALWC by HSRL. A positive correlation between the ALWC and the enhancement of aerosol scattering coefficient F calculated by the scattering coefficient at 525 nm measured in dry and ambient states proves the reliability of the ALWC obtained from HSRL. However, previous research has implied that fine mode particles dominating the total aerosol loading are required to precisely retrieve the ALWC, while the uncertainty of ALWC data will be large when the particle depolarization ratio is larger than 0.07. When it is less than 0.07, the ALWC derived from HSRL has high precision. By analyzing the aerosol property measurements (e.g., PM2.5, PM10, particle depolarization ratio, and scattering coefficient) near the surface, we found that ALWC contributes greatly to the deterioration of visibility. The variability of optical parameters in the vertical direction showed that ALWC significantly promotes the enhancement of aerosol extinction coefficients. Moreover, high ALWC significantly increases the scattering capacity of aerosols, leading to an enhanced cooling effect on the climate system.