Analysis of satellite remote sensing observations of low ozone events in the tropical upper troposphere and links with convection

Satellite observations from three instruments (Microwave Limb Sounder, Optical Spectrograph and Infrared Imaging System, and Atmospheric Chemistry Experiment Fourier Transform Spectrometer) reveal coherent patterns of low ozone events (<20 ppb) in the tropical upper troposphere. Using a chemical transport model (GEOS-Chem), we find that these events result from deep convective processes that rapidly transport air with low ozone concentrations from the marine boundary layer. These events occur with greater frequency over the tropical South Pacific warm pool, which is consistent with ozonesonde observations. The satellite observations indicate spatial shifts in the frequency of low ozone events that we attribute to changes in convection. As the location of the warm pool shifts eastward during El Nino events, the location of the most frequent low ozone events in the satellite record follows. Mapping of low ozone events over time reveals eastward propagating systems resembling the Madden-Julian Oscillation. These observations and analyses strengthen the link between deep convection and ozone concentrations in the tropical upper troposphere.