Comparison between Day/Night Time Aerosol Properties at a Site in Beijing

Abstract:

Knowledge of nocturnal aerosol properties is still limited due to the lack of effective means to observe aerosols during nighttime. We identified differences and difference mechanisms between day/night aerosol properties in different seasons measured at Peking University site in Beijing. Aerosol optical depth peak value appears in the morning and evening. Angstrom exponent value during daytime is much higher than nighttime, indicating larger particle size at night. Different seasons are characterized by different daily scattering coefficient cycles, while nighttime shows larger absorption coefficient and single scattering albedo in all seasons. Besides, daytime aerosol scale height is larger than nighttime, suggesting higher daytime boundary layer height. The differences between day/night aerosol properties are mainly attributed to aerosol sources and atmospheric conditions. Our study provides possible factors to take into consideration for research and modeling of day/night time aerosols in the future.