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Graphic: ACI Aerosol Climate Banner

Aerosol Formation, Aging, and Transport

Focus Area Lead: Jerome Fast

Graphic show sources of direct radiative forcing and indirect radiative forcing
Aerosol life-cycle (adapted from R. Zaveri)

Atmospheric aerosols usually only last for a few days, in contrast to greenhouse gases which, once released, tend to remain in the atmosphere for years or even decades. Because they last so much longer, greenhouse gases will tend to be evenly spread out over the planet, making it easier to predict their impact on climate. Aerosols, on the other hand, tend to be more localized, as are their climate impacts. The type and amount of aerosols in the atmosphere vary greatly from day to day and place to place. Because aerosols vary so much over relatively short spatial and temporal scales, it becomes harder to interpret the net impact aerosols have on global climate.

The formation of aerosol particles, their changes within the atmosphere, and their transport and removal are key processes in determining particle properties and concentrations, which in turn determine the direct and indirect impacts on the Earth's energy balance. Characterization of aerosol formation, and of the evolution of their chemical, microphysical, and optical properties throughout the aerosol life cycle are critical components of climate model development.

There are many gaps in fundamental knowledge and measurement capabilities associated with aerosol chemistry and subsequent cloud interactions. While it is known that many aerosols form from gas-phase precursors, relatively little is known about the precise chemical mechanisms by which these new aerosols form. We lack adequate descriptions of many relevant processes to incorporate them in regional and global-scale models. The Aerosol Climate Initiative addresses these gaps through the development of innovative modeling frameworks, including a process model that will simulate the growth and aging of particles in complex chemical environments, and an improved version of the current WRF-Chem model.

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