26 October 2011 Retrieval of aerosol and cloud properties using multiwavelength elastic-Raman lidar
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Abstract
The aerosol-cloud interaction is a complex and critical process in assessing the climate radiative effects of aerosol and cloud. Lidar can simultaneously measure the range-resolved distribution of aerosol-cloud with the high spatial-temporal resolution, and hence provides the opportunity to explore the cloud-aerosol optical properties and their interaction. Their interactions have been indicated by the significant variation of optical properties and droplet size of aerosol and cloud at the cloud vicinity or edges. But due to dramatic non-linear or irregular variation of lidar returns by the cloud, the evaluation of lidar algorithm deriving cloud extinction coefficient becomes quite important especially at the edges because the common algorithms may result in the artificial influence on the retrievals of cloud extinction and extinctionto- backscatter ratio (e.g. lidar ratio or S-ratio). In particular, the relationships of water cloud optical properties with the droplet size are simulated which include lidar ratio, color ratio and extinction ratio are used and general trends with measurements are demonstrated. To obtain color ratios (355/1064), a good calibration procedure for the 1064nm channel is required and we show that calibration errors using low water drop clouds allow absolute calibration < 10%. Preliminary results seem to indicate that small pre-nucleated droplets form at the aerosol - cloud boundary which is consistent with aerosol uptake into clouds. In addition, we also explore the increase in aerosol lidar-ratio below cloud indicative of hygroscopic growth.
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Yonghua Wu, Lina Cordero, Chuen-meei Gan, Barry Gross, Fred Moshary, Sam Ahmed, "Retrieval of aerosol and cloud properties using multiwavelength elastic-Raman lidar", Proc. SPIE 8177, Remote Sensing of Clouds and the Atmosphere XVI, 81770M (26 October 2011); doi: 10.1117/12.916579; https://doi.org/10.1117/12.916579
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