In Situ Particle Asymmetry Factor Monitor

Aerosol particles affect the radiative balance of the earth directly, by scattering and absorbing solar and terrestrial radiation, and indirectly, by acting as cloud condensation nuclei. It is now recognized that the atmospheric loading of aerosols generated through human activities can exert an influence on the earth's radiation budget comparable in magnitude with greenhouse gases. However, the uncertainties in the current understanding of aerosol direct and indirect forcing "limit the ability to quantify human influences on climate change". We propose to design, construct and test a monitor suitable for ambient monitoring which is capable of directly measuring the angular distribution of light scattered from the aerosol fraction and therefore the asymmetry parameter, g. The asymmetry parameter, which is a key input parameter in radiative forcing models, cannot at present be measured directly and must be inferred from other measurements.