The atmospheric electric conductivity measurements made over the Indian Ocean with a Gerdien's apparatus mounted aboard MV Polarbird during the XVI Indian Scientific Expedition in 1996--1997 are reported. Simultaneous three-hourly measurements of aerosol concentrations of 13--1000 nm size and some meteorological parameters are also reported. Latitudinal variation of conductivity along the cruise route shows a minimum at ~28¿S. Further, the variations in conductivity in the 10¿N--20¿S and 60¿--70¿S latitudinal belts show opposite trends on the outward and return cruises, which fall near to the onset and withdrawal phases of the northeast monsoon season, respectively. The results are explained on the basis of the well-known northward shift of the subsidence leg of the southern Hadley cell and of the position of the Intertropical Convergence Zone during the months of March--April in this region and the observations of the cyclonic systems near the continent of Antarctica during the period of outward cruise.