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GEMS Aerosol (Global Earth-system Monitoring using Satellite and in-situ data)
Alexander Mangold, Bart De Paepe, Hugo De Backer, Steven Dewitte
Royal Meteorological Institute of Belgium
3, Avenue Circulaire
1180 Uccle
Contact: Alexander Mangold
Schematic overview of the GEMS project.
GEMS - Objectives
The GEMS project has been started in May 2005, was funded by the European Commission within FP 6 and has come to a successful end in May 2009. GEMS is led by the European Centre for Medium-Range Weather Forecast (ECMWF), comprises 17 European research institutes, 10 regional modelling centres, 2 environmental protection agencies, and has been established to develop a real-time operational assimilation and forecast capability of aerosols, greenhouse gases and reactive gases. This new European operational system will be an extension of current data assimilation and forecast capabilities for Numerical Weather Prediction. It will also provide the initial and boundary conditions for operational regional air-quality and ‘chemical weather’ forecast systems across Europe. Satellite data will be a major source of information for assimilation. Ground-based observations and other satellite data will be used for validation and evaluation. As such, GEMS will be a major contribution to the GMES initiative (Global Monitoring for Environment and Security) launched a few years ago by the European Union and the European Space Agency.
GEMS-AER - Aerosol Sub-Project
RMIB contributes within GEMS to the Aerosol Sub-Project. The figure above illustrates schematically the links and the flow of data and information between the main elements of the GEMS system: Global Reactive Gases (GRG), Greenhouse Gases (GHG), Global Aerosol (AER), Regional Air Quality (RAQ), and the global atmospheric assimilation system at ECMWF.
GEMS-AER will provide operational aerosol products for a variety of end-users (e.g. modeling radiative transfer, air-quality). An improved and explicit representation of aerosols in forecasting models will have several positive impacts. The reduction of the uncertainty of the direct and indirect aerosol radiative effects is considered as a priority in climate change assessments. It will also provide key informations relevant to the UN Convention on Long-Range Trans-boundary Air Pollution.
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RMIB Contribution
The ground observations group of RMIB will contribute with the determination of the total aerosol optical depth (AOD) in the UV-B (320 nm) from direct sun observations with Brewer spectrophotometers, two of them located at RMIB, Uccle. An algorithm to retrieve AOD from Brewer instruments has recently been developed at RMIB (Cheymol & De Backer, 2003). It is the aim to collect data from as many stations as possible from the global network of Brewer instruments. The above-mentioned algorithm can then be applied to create AOD time series at the specific wavelengths in the UV. These aerosol data will be exploited for the validation of aerosol optical depth products from the assimilation runs of the ECMWF Numerical Weather Prediction model.
The satellite group of RMIB will contribute with the detection of aerosols from SEVIRI (Spinning Enhanced Visible and InfraRed Imager) images. Due to the combination of its different spectral channels, the SEVIRI instrument on board the MSG-1 (Meteosat Second Generation) satellite allows for the distinction between clouds and aerosols. The RMIB-SEVIRI aerosol product includes AOD at 630, 830, and 1610 nm, with a spatial resolution of 9 x 9 km and a time resolution of 15 min. The SEVIRI aerosol product is available over ocean only, for the SEVIRI disk and from February 2004 onwards.
Results
GEMS came to a successful end in May 2009 and is succeeded by the MACC project. Within GEMS, multi-year re-analyses for the individual GHG-, GRG-, AER-models were achieved, there is a common integrated re-analysis for the period 2003-2007, and a near real-time integrated analysis and forecast model for GHG, GRG and AER. In addition, the analysis is used as boundary condition for 10 European regional air quality models, which in return produce ensemble and individual predictions of air quality indicators. All these data and maps are online available via the GEMS web page. The model results were comprehensively evaluated, validated and compared to observations.