A Practical Guide to Atmospheric Simulation Chambers

The ability to predict the evolution of the atmosphere over a wide range of time scales (hours to decades) brings great benefits to society. Examples include short-term public warnings of hazardous air quality and the long-term evaluation of climate warming and policy effectiveness. Atmospheric predictions use complex models that are underpinned by observations and a sound understanding of the underlying processes, which include the interactions between atmospheric components and their environment. Atmospheric simulation chambers are among the most advanced tools for studying and quantifying atmospheric processes and are used to provide many of the parameters incorporated in air quality and climate models. Without chamber-derived parameters to constrain predictive models, any physico-chemical forecasts of the atmosphere are highly unreliable, both in the short-and long-term. The largest uncertainties in our current knowledge of atmospheric processes and their impact on air quality and climate change are associated with complex feed-back mechanisms in the Earth System. Understanding and quantifying those mech-anisms that are just becoming measurable are only possible through a synergistic approach that combines atmospheric observations, detailed simulation experiments and modelling. This methodology is the most efficient means of obtaining a quantitative understanding of physico-chemical transformations in the atmosphere and chamber studies are a key component of that approach. The level of scientific understanding of climate drivers, the health impacts of complex mixtures of air pollutants, and the interaction between the two is still evolving. Simulation chambers were originally created to study the impact of atmo-spheric processes on regional photochemistry. This approach has since been extended to understand particles formation, cloud microphysics and global warming. More recently, atmospheric simulation chambers have been applied to a wider range of research areas such as human health and cultural heritage. In all cases, a key objective is to work under conditions that are as realistic as possible.