Atmospheric aerosol particles are a major player in the earth system: they impact the climate by scattering and absorbing solar radiation, as well as regulating the properties of clouds. On regional scales aerosol particles are among the main pollutants deteriorating air quality. Capturing the impact of aerosols is one of the main challenges in understanding the changing climate. According to the Intergovernmental Panel on Climate Change (IPCC), aerosols have been the most important atmospheric cooling component in the industrial period. At the same time IPCC recognizes the predictions of aerosol impacts as the largest individual source of uncertainty in climate models. To pin down the effects of aerosols on climate and air quality, the processes governing their concentrations need to be understood and represented accurately in large-scale models. Atmospheric aerosol number budgets are governed by the ultrafine (< 100 nm in diameter) particles. Most of these particles have been formed from atmospheric vapours, and their fate and impacts are governed by the mass transport processes between the gas and particulate phases. These transport processes are currently poorly understood, particularly for the smallest nanoparticles. Correct representation of the aerosol growth/shrinkage by condensation/evaporation of atmospheric vapours is thus a prerequisite for capturing the evolution and impacts of aerosols.
I will start a research group that will address the major current unknowns in atmospheric ultrafine particle growth and evaporation. First, we will develop a unified theoretical framework to describe the mass accommodation processes at aerosol surfaces, aiming to resolve the current ambiguity with respect to the mass accommodation of atmospheric vapours. The growth of aerosol particles and cloud droplets is very sensitive to the mass accommodation coefficients, but this fundamental property is extremely poorly constrained even for pure water. Second, we will study the condensational properties of selected organic compounds and their mixtures. Organic compounds are known to contribute significantly to atmospheric aerosol growth, but the properties that govern their condensation, such as saturation vapour pressures and activities, are largely unknown. Third, combining our fundamental understanding on the mass transport at the gas-aerosol interface with atmospheric observations, we aim to resolve the gas and particulate phase processes that govern the growth of realistic atmospheric aerosol. Fourth, we will parameterise ultrafine aerosol growth, implement the parameterisations to chemical transport models, and quantify the impact of these condensation and evaporation processes on global and regional aerosol budgets.
The main expected outcome of this project is a quantitative description of atmospheric nanoparticle growth by organic vapour condensation, and its implications for climate and air quality. Besides completing the understanding of the atmospheric ultrafine particle evolution, future applications of our results extend from droplet and ice crystal growth in clouds to any industrial or scientific application that exploits generation and manipulation of nanoparticles by vapour condensation/evaporation.
