Lidar aerosol ratios at 1 and 10 microns

Lidar (extinction-to-backscatter) ratios are computed at 0.55, 1 and 10 μm, based upon a recently published summary of the physicochemical properties of climatically relevant aerosol species. The results agree very well with previously measured values in the literature, indicating that low S_a values for desert dust (15-30) and maritime (30-45) aerosols are clearly distinguishable from biomass burning (55-65) and urban/industrial pollution (55-80). The results show that most aerosol types can be discriminated by their absorption and scattering characteristics through use of spectral lidar ratios, except between biomass burning and pollution aerosols. Predictions of on- and off-axis scattering in the presence of these aerosol types illustrate the range of signal that may be expected in a bistatic lidar system in such cases, and indicate that bistatic lidar may be successfully used to detect a source lidar signal and discriminate the aerosol species present. These findings strongly suggest that a combination of passive and active remote sensing systems operating simultaneously (e.g., ground-based sky radiance and bistatic lidar), would be capable of directly measuring the absorption and scattering characteristics required to describe the optical behaviour of the aerosol with vertical resolution. This is expected to be of great utility to climate researchers or other communities interested in comprehensively measuring atmospheric optical properties.