Some atmospheric aerosol characteristics as determined from laser angular scattering measurements at a continental urban station

Abstract

A bistatic continuous wave Argon ion lidar system has been used to collect information on the variation of laser return signal strength from the lower atmosphere with scattering angles at a fixed altitude of scattering. Lidar data collected on 50 clear sky days during the period of April 1987 - December 1995 at a continental tropical urban station have been used for the study. The experimental data have been compared with the theoretically computed differential Mie scattering cross sections at the common scattering angles to determine the most probable value of size index, n, and the complex index of refraction, m, applicable to the environment over the observing site by adopting a library-search method and simple statistical tools. The study showed that the most frequently occurring aerosol type at the location is dust-like with a most probable value of size index 4.5. Retrieval of aerosol number concentration, using this information together with the experimental values of scattered signal strength, yields an average concentration value in the range of 2 - 3 x 10³ cm^-3 in the atmospheric layer close to the surface.