Intra-seasonal variability in tropospheric ozone and water vapor in the tropics

Nearly two years of tropospheric O-3 and H2O data from the Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) instruments are analyzed to study the characteristics of intra-seasonal oscillation (ISO) of 20-100 day periods. The analysis shows the presence of ISO signals in O-3 and H2O throughout much of the tropics including the north Atlantic not shown in previous studies. ISO variability west of the dateline appears as a manifestation of eastward propagation of the Madden-Julian Oscillation (MJO). Time series of tropospheric O-3 and H2O are negatively correlated throughout much of the tropics, and mostly over ocean. This suggests lofting of air from convection as a basic driving mechanism, with convection transporting low amounts of O-3 and high amounts of H2O upwards from the boundary layer. ISO/MJO related changes in O-3 and H2O are a major source of variability and often exceed 25% of background concentrations.