Abstract
Abstract. A workshop was held in the framework of the ACCENT (Atmospheric Composition Change – a European Network) Joint Research Programme on "Aerosols" and the Programme on "Access to Laboratory Data". The aim of the workshop was to hold "Gordon Conference" type discussion covering accommodation and reactive uptake of water vapour and trace pollutant gases on condensed phase atmospheric materials. The scope was to review and define the current state of knowledge of accommodation coefficients for water vapour on water droplet and ice surfaces, and uptake of trace gas species on a variety of different surfaces characteristic of the atmospheric condensed phase particulate matter and cloud droplets. Twenty-six scientists participated in this meeting through presentations, discussions and the development of a consensus review. In this review we present an analysis of the state of knowledge on the thermal and mass accommodation coefficient for water vapour on aqueous droplets and ice and a survey of current state-of the-art of reactive uptake of trace gases on a range of liquid and solid atmospheric droplets and particles. The review recommends consistent definitions of the various parameters that are needed for quantitative representation of the range of gas/condensed surface kinetic processes important for the atmosphere and identifies topics that require additional research.
Highlights
Introduction and motivation1.1 Why are trace gas uptake processes important?Trace gas uptake by a variety of condensed phase materials on the Earth’s surface, including vegetation, rock, soil, ice, snow, fresh and marine surface waters, buildings and paved surfaces can play an important role in the transformation and environmental fate of many atmospheric species
The use of multiple phenomenological models and inconsistent terminology raises several key questions: 1. Are the different definitions, terminologies, parameters, and model formalisms fully consistent and equivalent? What are the exact relations between the different terms, parameters, and formalisms? Which of them are best suited for application in analysis of experimental trace gas uptake data, detailed small-scale atmospheric process models and in simplified large-scale atmospheric models?
Trace gas exchange between the gas phase and solid particle or liquid droplet condensed phases are driven by thermodynamics, but are achieved by elementary kinetic and transport processes occurring at the phase interface and, sometimes, in the underlying bulk phase
Summary
Trace gas uptake by a variety of condensed phase materials on the Earth’s surface, including vegetation, rock, soil, ice, snow, fresh and marine surface waters, buildings and paved surfaces can play an important role in the transformation and environmental fate of many atmospheric species. Heterogeneous uptake by PM and cloud droplets, often coupled with surface and/or bulk phase reactions, can significantly alter the distribution of reactive atmospheric gases. The uptake of trace gases, including water vapour, impacts important physical properties of atmospheric PM, such as size, optical properties, and ability to nucleate cloud droplets. These properties all impact the direct interaction of PM with atmospheric radiation or their ability to alter cloud formation and evaporation rates, which influence atmospheric radiative fluxes as well as precipitation patterns. The following discussion will focus on the interaction of trace gases with atmospheric cloud droplets and PM, some of the material is pertinent to trace gas interactions with materials at the Earth’s surface
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