VATIS UPDATE Article

A team of researchers from Université Libre de Bruxelles (ULB), Belgium, National Center for Atmospheric Research, the United States, Sorbonne Universités, France, and Institute of Technology, Cambridge, the United States, assessed how daily ozone (O3) measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A platform can contribute to the analyses of the processes driving O3 variability in the troposphere and the stratosphere and, in the future, to the monitoring of long-term trends.

The temporal evolution of O3 during the first 6 years of IASI (2008-2013) operation is investigated with multivariate regressions separately in four different layers, by adjusting to the daily time series averaged in 20° zonal bands, seasonal and linear trend terms along with important geophysical drivers of O3 variation (e.g. solar flux, quasi-biennial oscillation (QBO)). The regression model is shown to perform generally very well with a strong dominance of the annual harmonic terms and significant contributions from O3 drivers, in particular in the equatorial region where the QBO and the solar flux contribution dominate.

More particularly, despite the short period of the IASI data set available up to now, two noticeable statistically significant apparent trends are inferred from the daily IASI measurements: a positive trend in the upper stratosphere, which is consistent with other studies suggesting a turnaround for stratospheric O3 recovery, and a negative trend in the troposphere at the mid-latitudes and high northern latitudes, especially during summer and probably linked to the impact of decreasing ozone precursor emissions. The research findings have been published in Atmospheric Chemistry and Physics.