Determination of Nocturnal Aerosol Properties from a Combination of Lunar Photometer and Lidar Observations

摘要

Aerosol plays a key role in the assessment of global climate change and environmental health, while observation is one important way to deepen the understanding of aerosol properties. In this study, the new instrument - lunar photometer is used to measure moonlight and nocturnal column aerosol optical depth (AOD, τ) is retrieved. The AOD algorithm is tested and verified with sun photometer both in high and low aerosol loading. Angstroem exponent (α) and fine/coarse mode AOD (τ_f, τ_c) is derived from spectral AOD. The column aerosol properties (τ, α, τ_f, τ_c) inferred from the lunar photometer is analyzed based on two month measurements in Beijing. Micro-pulse lidar has advantages in retrieval of aerosol vertical distribution, especially in night. However, the typical solution of lidar equation needs lidar ratio (ratio of aerosol backscatter and extinction coefficient) assumed in advance (Fernald method), or constrained by AOD. Yet lidar ratio varies with aerosol type and is not easy to determine, and AOD is taken from daylight measurement, which is not consistent when aerosol loading is different from day and night. In this paper, the nocturnal AOD measurement from lunar photometer combined with Mie scattering lidar observations to invert aerosol extinction coefficient (σ) profile in Beijing is discussed.