Measurements of the atmospheric electric field and conductivity made over Indian Ocean during December 96 - January 97

Abstract

Observations of the atmospheric electric field and conductivity are made over the Indian Ocean during the pre-Indian Ocean Experiment (pre-INDOEX) cruise of ORV Sagar Kanya in December '96-January '97. The average of the diurnal variations of electric field on 6 fair-weather days during the cruise shows a single periodic variation with a maximum at 1100 GMT and a minimum at 0300 GMT. Its possible implications with respect to the global electric circuit are discussed. Electric conductivity is generally less in the northern hemisphere and increases 2-3 times in the southern hemisphere. Background aerosol concentrations have been calculated from the observed values of the electrical conductivity and discussed with respect to the local meteorological conditions in the region. The results show aerosol concentration of 1300 to 1800 particles/cm³ near the coastline in the northern hemisphere which slowly decrease as one goes away from the coast. Comparatively much lower aerosol concentrations of about 800 particles/cm³ are observed at 12-14°S in the pristine air of the southern hemisphere. Observations indicate a change of 2 to 4 times in the background aerosol pollution since the Carnegie measurements in this area in the second decade of this century.