Online coupled regional meteorology chemistry models in Europe: current status and prospects

Abstract

The simulation of the coupled evolution of atmospheric dynamics, pollutant transport,chemical reactions and atmospheric composition is one of the most challenging tasksin environmental modelling, climate change studies, and weather forecasting for thenext decades as they all involve strongly integrated processes. Weather strongly influences air quality (AQ) and atmospheric transport of hazardous materials, while atmo-spheric composition can influence both weather and climate by directly modifying theatmospheric radiation budget or indirectly affecting cloud formation. Until recently, how-ever, due to the scientific complexities and lack of computational power, atmosphericchemistry and weather forecasting have developed as separate disciplines, leading to the development of separate modelling systems that are only loosely coupled.The continuous increase in computer power has now reached a stage that enablesus to perform online coupling of regional meteorological models with atmosphericchemical transport models. The focus on integrated systems is timely, since recentresearch has shown that meteorology and chemistry feedbacks are important in the context of many research areas and applications, including numerical weather predic-tion (NWP), AQ forecasting as well as climate and Earth system modelling. However,the relative importance of online integration and its priorities, requirements and lev-els of detail necessary for representing different processes and feedbacks can greatlyvary for these related communities: (i) NWP, (ii) AQ forecasting and assessments, (iii) climate and earth system modelling. Additional applications are likely to benefit fromonline modelling, e.g.: simulation of volcanic ash or forest fire plumes, pollen warnings,dust storms, oil/gas fires, geo-engineering tests involving changes in the radiation bal-ance.The COST Action ES1004 – European framework for online integrated air quality and meteorology modelling (EuMetChem) – aims at paving the way towards a new gener-ation of online integrated atmospheric chemical transport and meteorology modellingwith two-way interactions between different atmospheric processes including dynamics, chemistry, clouds, radiation, boundary layer and emissions. As its first task, wesummarise the current status of European modelling practices and experience withonline coupled modelling of meteorology with atmospheric chemistry including feed-back mechanisms and attempt reviewing the various issues connected to the differentmodules of such online coupled models but also providing recommendations for coping with them for the benefit of the modelling community at large.