Physical properties of the Indian aerosol plume derived from six-wavelength lidar observations on 25 March 1999 of the Indian Ocean Experiment

Abstract

A major pollution outbreak from the Indian subcontinent was observed with a six-wavelength aerosol lidar at Hulule island (4.1 degrees N, 73.3 degrees E) on 25 March 1999 during the Indian Ocean Experiment. From the observed backscatter and extinction data, vertical profiles of physical particle properties were determined. Effective radii between 0.14 and 0.22 mu m, complex refractive indices of about 1.65 in real part and between 0.03i and 0.08i in imaginary part, and single-scattering albedos between 0.79 and 0.86 at 532 nm suggest anthropogenic activities and biomass burning as source of the particles. First estimates from radiative-transfer calculations show a cooling of -6.4 W/m(2) at the top of the atmosphere and -70 W/m(2) at ground level.