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 an application in a global atmospheric model, we discuss the technical aspects of the implementation in the European Centre for Medium Range Weather Forecasts Integrated Forecasting System (ECMWF-IFS) and the impact of the new climatology on the medium-range weather forecasts and 1-year simulations. The new aerosol climatology was derived by combining a set of model simulations with constrained meteorological conditions and an atmospheric composition reanalysis for the period 2003–2013 produced by the IFS. The aerosol fields of the reanalysis are constrained by assimilating the aerosol optical thickness (AOT) retrievals product by the Moderate Resolution Imaging Spectroradiometer (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 the direct aerosol radiative effect compared to the climatology previously implemented, which have a small but non-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.
Highlights
Aerosols have an important impact on the radiative budget of the Earth–atmosphere system
This work documents a new monthly-mean climatology of aerosol distribution based on the Interim reanalysis from Copernicus Atmosphere Monitoring Service (CAMS) (CAMSiRA, Flemming et al, 2017) and its control run
The user can associate the radiative properties of choice with the aerosol distribution, and here we present results that used the bulk properties for each species computed for the 30 radiative bands of the ECMWF radiative scheme (Hogan and Bozzo, 2018)
Summary
Aerosols have an important impact on the radiative budget of the Earth–atmosphere system. The largest impact on weather the forecast skill of a prognostic aerosols scheme coupled to an NWP model is in case of events that are associated with large aerosol optical depths such as dust storms or wildfires In these situations a realistic representation of the aerosol distribution differs significantly from the average climatology, and it can improve forecasts locally, especially close to the surface. Both direct and indirect radiative effects were included, the latter impacting the number concentration of liquid cloud droplets according to Menon et al (2002) They found that compared to the TG97 climatology, the changes in medium-range, large-scale forecast skill caused by having the prognostic aerosols interacting with radiation and cloud microphysics were small, near-surface parameters showed local improvements. The aerosol climatology is intended for public use, and it will be available through the CAMS data service
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