LIDAR-DERIVED VARIATIONS IN THE BACKSCATTER-TO-EXTINCTION RATIO IN SOUTHERN-HEMISPHERE COASTAL MARITIME AEROSOLS

Lidar measurements were made of the optical properties of maritime aerosols from a tropical coastal site in north Queensland, Australia. From horizontal firings approximately 2 m over the ocean, data obtained during homogeneous conditions were used to derive the atmospheric extinction coefficient. During periods when the extinction and backscatter coefficients varied, but their ratio remained constant, it was possible to calculate this ratio and also to provide an independent calibration of the lidar. This calibration was then used to determine the backscatter-to-extinction ratio in periods when it was quite variable. This variability is related to variations in the meteorological and airmass data which were measured concurrently on the shore. Data obtained during a summer and a winter study are analysed.