The Influence of the Madden-Julian Oscillation on the Equatorial Tropospheric Ozone

The Madden-Julian Oscillation (MJO) is the dominant form of the atmospheric intra-seasonal oscillation, manifested by slow eastward movement (about 5 m/s) of tropical deep convection. This study investigates the MJO's impact on equatorial tropospheric ozone in satellite observations and chemical transport model (CTM) simulations. For the satellite observations, we analyze the Tropospheric Emission Spectrometer (TES) level-2 ozone profile data for the period of Jan 2004 to Jun 2009. It was found that deep convection related to the MJO decreases total tropospheric column ozone in the convective area. The equatorial tropospheric ozone anomalies propagate eastward at a similar phase speed of the convective anomalies (5 m/s). For the CTM simulations, we ran the Community Earth System Model (CESM) driven by the GOES-5 analyzed meteorological fields for the same data period as the TES measurements. Our analysis indicates that the simulated MJO-related equatorial tropospheric ozone variation is very similar to the satellite measurements with a correlation coefficient between the two ranging from 0.66 to 0.88 for the 8 phases of MJO. Analysis of the simulated ozone tendency terms indicates that deep convection decreases the ozone in the upper troposphere but increases the ozone in the middle troposphere; however, ozone chemistry increases ozone in the upper troposphere and decreases ozone in the middle troposphere.