Convective lofting links Indian Ocean air pollution to paradoxical South Atlantic ozone maxima

Abstract

We describe a broad resolution of the “Atlantic Parado” concerning the seasonal and geographic distribution of tropical tropospheric ozone. We highlight periods of significant maximum tropospheric O₃ for Jan.–April, 1999, exploiting satellite estimates and SHADOZ (Southern Hemisphere Additional Ozonesondes). Trajectory analyses connecting sondes and Total Tropospheric Ozone (TTO) maps suggest a complex influence from the Indian Ocean: beginning with mixed combustion sources, then low level transport, cumulonimbus venting, possible stratospheric input, and finally high-level transport to the west, with possible mixing over Africa. For the Jan.–March highest column-O₃ periods in the Atlantic, distinct sounding peaks trace to specific NO sources, especially lightning, while in the same episodes, recurring every 20–50 days, more diffuse buildups of Indian-to-Atlantic pollution make important contributions.