Cross-Instrument Validation and Investigation of Aerosol Optical Properties During and After COVID-19

Using the Multiwavelength Raman LiDAR (Light Detection and Ranging) system at CCNY, we investigated the optical properties of atmospheric particles and gasses for extended periods during the COVID-19 pandemic and after the pandemic. By emitting laser pulses at 355 nm, 532 nm, and 1064 nm, the LiDAR system allows us to measure vertical profiles of aerosol parameters such as backscatter and extinction coefficients, optical depth, LiDAR ratio, and Ångström exponent. The Ångström exponent is determined from the ratio of lidar returns at 532 nm and 1064 nm and provides size information about the particle size. This study is important for us to understand the effects of aerosols on the environment and health. The paper compares the variation of man-made aerosol emissions during the pandemic with the same variables after COVID restrictions were lifted. The modeled parameters in this study are aerosol optical properties and aerosol and its impact on radiative forcing. Furthermore, we utilize HYSPLIT backward trajectories, CIMEL sunphotometer, and microwave radiometer data to understand the aerosol sources and the impact of the atmospheric temperature, relative humidity, and water vapor on aerosol optical properties. The working principles behind each instrument are explained to better understand the used parameters in our model validations.