Examining ENSO-related variability in tropical tropospheric ozone in the RAQMS-Aura chemical reanalysis

Abstract. The El Niño–Southern Oscillation (ENSO) is a major driver of interannual variability in both tropical latitudes and midlatitudes and has been found to have a strong impact on the distribution of tropospheric ozone in the tropical Pacific in satellite observational datasets, chemical transport models, and chemistry–climate simulations. Here we analyze interannual variability in tropical tropospheric ozone by applying composite analysis, empirical orthogonal function (EOF) analysis, and multiple linear regression to the Real-time Air Quality Modeling System (RAQMS) Aura (RAQMS-Aura) chemical reanalysis. As shown in similar studies, the dominant mode of interannual variability in tropical tropospheric ozone is driven by ENSO. ENSO composites show that the ENSO signature in tropospheric ozone is strongest near the tropopause. We also show an enhancement in tropical ozone over the maritime continent below 700 hPa during El Niño that is dependent on the magnitude of the biomass burning emissions in the region. We reconstruct the ENSO variability in tropical tropospheric ozone through a multiple linear regression of principal components for precipitation and CO. The multiple linear regression quantifies that variability in biomass burning contributes to ENSO variability in tropical tropospheric ozone, though the dominant driver is convective precipitation.