Elucidating the Impact of Aerosols on Cloud Physics and the North Atlantic Regional Climate (EIRE Climate)

Final Report from EPA ERTDI-funded project 2008-FS-29-M1

Summary: STRIVE Report 52 - Robert J. Flanagan and Colin D. O’Dowd

Aerosols affect the Earth’s climate through their interaction with clouds by acting as sites on which cloud droplets can form. These interactions alter the cloud’s microphysics and lifetime. This effect is of critical importance as clouds perform a major role in maintaining the Earth’s radiation balance primarily by reflecting sunlight back into space and absorbing the infrared radiation emitted by the Earth. The number and size of droplets are the key factors influencing how much radiation clouds reflect back into space.

A cloud droplet activation parameterisation has been implemented in the REMOTE (REgional MOdel with Tracer Extension) regional climate model. The parameterisation provides a robust computationally efficient treatment of aerosol cloud interactions. There are large uncertainties in the indirect effect due
to the complex aerosol–cloud interactions involved.REMOTE, including the newly implemented cloud droplet nucleation scheme, provides a useful tool to study the indirect effect of aerosols.

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