Introducing IFS-CB05-BASCOE-GLOMAP (ICBG): A Coupled Tropospheric and Stratospheric Aerosol and Chemistry Option for the ECMWF IFS

Within the Copernicus Atmosphere Monitoring Service (CAMS), operated by ECMWF on behalf of the European Union, ECMWF's Integrated Forecasting System (IFS) is run with a tropospheric chemistry scheme (CB05), a simplified linear stratospheric ozone scheme, and a hybrid bin/bulk aerosol scheme, to produce both operational forecasts and reanalyses of atmospheric composition. The IFS also has the option to run with additional modules for chemistry (BASCOE for the stratosphere, MOZART and MOCAGE for the troposphere) and for aerosol (the GLOMAP-mode aerosol scheme).

As part of the continuous development of the CAMS global forecasting system, a new combined tropospheric-stratospheric chemistry-aerosol system denoted IFS-CB05-BASCOE-GLOMAP (ICBG) has been implemented, which integrates these different capabilities, including the addition of sulphur species in the stratospheric chemistry scheme for interactive stratospheric aerosol capability.

This new ICBG system has been tested in volcanically quiescent conditions and three volcanic aerosol case studies: the 1991 Pinatubo eruption, the April 2015 Calbuco eruption and the recent eruption of the Raikoke in June 2019. Comparisons are made for the Calbuco and Raikoke volcanic cases with simulations carried out without coupling the tropospheric and stratospheric chemistry, showing the benefits of the combined aerosol-chemistry approach. Results and evaluation of two case studies will be presented.