AEROSOL-PROFILE MEASUREMENTS IN THE LOWER TROPOSPHERE WITH 4-WAVELENGTH BISTATIC ARGON-ION LIDAR

The scattering properties of aerosols over a tropical urban station, P une, India, (18 degrees 32' N, 73 degrees 51' E, 559 m above mean sea level), are studied with a bistatic, multiwavelength, continuous-wave, argon-ion lidar. The scattered-intensity profiles (up to 1000 m above ground level) measured at four wavelengths (0.4765, 0.4880, 0.4965, a nd 0.5145 mu m) of the laser during November 1987-March 1990 revealed certain spectral dependence, in conformity with the Mie theory of aero sol particles. Methods for retrieving the bulk as well as the height v ariation of aerosol-size distribution from the inversion of angular di stribution of scattered-light-intensity measurements from a constant a ltitude and scattered-intensity vertical-profile measurements at diffe rent wavelengths are explained. Results obtained from these approaches are presented and compared with results reported by other investigato rs. The deviations in the results are discussed in relation to the ass umptions involved and the terrain-atmospheric conditions at the experi mental station. It is found that the aerosol-size-distribution paramet er is altitude dependent beside its dependence on refractive index and wavelength of incident radiation. The results of the study suggest th at the information content from bistatic, multiwavelength laser scatte ring measurements is useful for inferring aerosol-size distribution.