Water adsorption on model atmospheric clay minerals as a function of relative humidity: Application of experimental results to Adsorption Activation Theory

The indirect aerosol effect on climate includes radiative effects from aerosol particles that take up water and form cloud droplets or alter the radiative properties and lifetimes of clouds. This effect is currently one of the largest uncertainties in understanding climate change. Natural aerosols, including mineral dust, have received little attention with respect to their contribution to indirect forcing largely due to the difficulties arising from laboratory measurements. In the past, atmospheric climate models have neglected the potentially significant effect of mineral dust aerosol on the indirect climate effect. However, a number of recent studies have revealed the importance of adsorbed water on the surface of minerals for predicting their CCN activity. Laboratory water adsorption measurements on the three most abundant clay minerals found in the atmosphere using an ATR-FTIR equipped with a flow cell will be reported. The FHH adsorption isotherm model was applied to the experimental results and resulting adsorption parameters have been used in FHH-Adsorption Activation Theory (FHH-AT) in an effort to provide adsorption parameters to predict CCN activation of mineral dust aerosol in the atmosphere.