A new synergistic approach for tropospheric ozone profiling

Tropospheric ozone is a significant greenhouse gas (GHG) formed and destroyed by chemical reactions involving other atmospheric species and a key constituent for understanding the interactions between climate and chemistry. In contrast to most GHGs, tropospheric ozone is produced photo-chemically via its precursors, notably nitrogen oxides (NOx), carbon monoxide (CO), CH4 and non-methane hydrocarbons, all of which have large anthropogenic sources. Crucial uncertainties, however, remain in the assessment of the tropospheric ozone budget, its precursors, and the chemical and physical processes involved. Large spatial and temporal variability is observed in tropospheric ozone, resulting from important regional differences in the factors controlling its concentration. For all these reasons, accurate global measurements of ozone vertical profiles in the troposphere are essential. AURORA (Advanced Ultraviolet Radiation and Ozone Retrieval for Applications) is a three-year project (ending in July 2019) supported by the European Union in the frame of its H2020 Call EO-2-2015. Its overarching objective is to simulate the provision of synergistic data products, having unprecedented accuracy, for the vertical profiling of atmospheric ozone and to assess their quality with respect to the one expected for the operational products of the geostationary (GEO) mission Sentinel-4 and of the Low Earth Orbit (LEO) missions Sentinel-5p and Sentinel-5. In particular, the main scientific purpose of AURORA is to investigate the potential of synergistic exploitation of complementary ozone measurements acquired in different spectral regions - from the UV over the visible to the thermal infrared - through the assimilation of fused GEO and LEO ozone profile products resulting from application of the innovative method of complete data fusion. The impact of combining complementary capabilities of the atmospheric Sentinels observations, especially in terms of vertical sensitivity, might result in advanced performances that are of specific relevance for tropospheric ozone monitoring. In the frame of the project it has been demonstrated that the complete data fusion method is able to reduce the complexity of managing the high volume of Copernicus S-4 and S-5 data and to increase its quality with respect to the operational outcome of individual instruments. In particular, the fused products show higher degrees of freedom and an enhanced vertical sensitivity. In this project, the 3D ozone analyses and forecasts obtained from the data assimilation systems after assimilating the fused ozone observations are used to derive tropospheric ozone columns and profiles. An extensive ozone product validation system has been developed in the frame of the project to assure that the AURORA tropospheric ozone and data products will be warily verified and documented by means of in-depth QA/validation studies. In this presentation we will discuss the first results of the AURORA synergistic approach, based on data fusion and assimilation, applied to the tropospheric ozone profiling.