An aerosol climatology for global models based on the tropospheric aerosol scheme in the Integrated Forecasting System of ECMWF

Abstract

Abstract. An aerosol climatology to represent aerosols in the radiation schemes of Global Atmospheric Models was recently developed. We derived the climatology from a reanalysis of atmospheric composition produced by the Copernicus Atmosphere Monitoring Service (CAMS). As an example of application into a global atmospheric model, we discuss the technical aspects of the implementation in the Integrated Forecasting System of European Centre for Medium Range Weather Forecasts (ECMWF-IFS) and the impact of the new climatology on the medium-range weather forecasts and one-year simulations. The new aerosol climatology was derived by combining a set of model simulation with constrained meteorological conditions and an atmospheric composition reanalysis for the period 2003–2014 produced by the IFS. The aerosol fields of the re-analysis are constrained by assimilating Aerosol optical thickness (AOT) retrievals product by the MODIS instruments. In a further step, we used modelled aerosol fields to correct the aerosol speciation and the vertical profiles of the aerosol reanalysis fields. The new climatology provides the monthly-mean mass mixing ratio of five aerosol species constrained by assimilated MODIS AOT. Using the new climatology in the ECMWF-IFS leads to changes in direct aerosol radiative effect compared to the climatology previously implemented, which have a small, but non-negligible impact on the forecast skill of large-scale weather patterns in the medium-range. However, details of the regional distribution of aerosol radiative forcing can have a large local impact. This is the case for the area of the Arabian Peninsula and the northern Indian Ocean. Here changes in the radiative forcing of the mineral dust significantly improve the Summer Monsoon circulation.