Summertime tropospheric ozone assessment over the Mediterranean region using the thermal infrared IASI/MetOp sounder and the WRF-Chem model

摘要

Over the Mediterranean region, elevated tropospheric ozone (O₃) valuesare recorded, especially in summer. We use the thermal Infrared AtmosphericSounding Interferometer (IASI) and the Weather Research and ForecastingModel with Chemistry (WRF-Chem) to understand and interpret the factors andemission sources responsible for the high O₃ concentrations observed inthe Mediterranean troposphere. Six years (2008–2013) of IASI data have beenanalyzed and results show consistent maxima during summer, with an increase of up to22% in the [0–8] km O₃ column in the eastern part of the basincompared to the middle of the basin. We focus on summer 2010 to investigatethe processes that contribute to these summer maxima. Using two modeledO₃ tracers (inflow to the model domain and local anthropogenicemissions), we show that, between the surface and 2 km, O₃ is mostlyformed from anthropogenic emissions, while above 4 km it is mostly transportedfrom outside the domain or from stratospheric origins. Evidence ofstratosphere-to-troposphere exchange (STE) events in the eastern part of the basinis shown, and corresponds to a low water vapor mixing ratio and highpotential vorticity.