Towards the next CAMS reanalysis of atmospheric composition

Global reanalyses of atmospheric composition (AC) have become a valuable data source to study trends of aerosols, reactive gases, and greenhouse gases. These reanalyses are produced by data assimilation of satellite retrievals of atmospheric composition with atmospheric composition models. The AC reanalysis data are consistent gridded data sets at high temporal resolution (“maps without gaps”) covering decades. Reanalyses are well suited for the study of trends as the users do not have to deal with spatial and temporal gaps in the assimilated observations and their inter-instrument biases. However, the trends and variability of the atmospheric composition fields in AC reanalysis are also influenced by the trends of the model input data such as emissions from anthropogenic sources and wildfires as well as from the meteorological conditions and changes in the availability of the assimilated satellite data.

The Copernicus Atmosphere Monitoring Service (CAMS, atmosphere.copernicus.eu) has produced several AC reanalyses for the period starting in 2003 by assimilating satellite retrievals of atmospheric composition with the ECMWF model. The latest version is the CAMS Reanalysis (EAC4, Inness et al 2019) which is continued in near-real-time with a delay of a few weeks. It has been used for a wide range of applications such as the monitoring of the ozone hole, trends of surface PM2.5 and AOD, tropospheric ozone, and carbon monoxide.

CAMS currently prepares the production of a new AC reanalysis (EAC5). EAC5 has a more advanced modelling approach that also includes stratospheric chemistry and a wider range of secondary aerosols than EAC4. Further, more satellite retrievals in particular from the TropOMI instrument will be assimilated. In this presentation we will give a status update of the preparations for EAC5 and present the efforts on modelling and data assimilation to ensure the production of a consistent data set. Results of scouting analysis and model simulations will be shown to indicate the expected improvements of EAC5 with respect to EAC4.