Vertical profiling of the Indian aerosol plume with six-wavelength lidar during INDOEX: A first case study



During the Intensive Field Phase (IFP) of the Indian Ocean Experiment (INDOEX) lasting from 15 February to 26 March 1999, a large number of pollution outbreaks from India and southeast Asia were observed with a unique six-wavelength aerosol lidar at Maldives International Airport, Hulule (4.1°N, 73.3°E). An example is presented here. Above the polluted marine boundary layer a 3-km deep aerosol layer was advected from the Indian subcontinent. The aerosol optical depths of the marine boundary layer and the free-troposphere layer were approximately 0.2 and 0.4 at 532 nm, respectively. Inversions using spectrally resolved particle backscatter and extinction data indicate an effective particle radius of 0.17 µm, volume and surface concentrations around 13 µm³ cm−3 and 600 µm² cm−3, respectively, and considerable absorption by the free-tropospheric particles.