Abstract
There is growing evidence that distributions of small hydrated ions, or the neutral water clusters which these ions produce, are implicated in the continuum-like spectral absorption of atmospheric water vapor in the infrared and at longer wavelengths. Three categories of evidence are examined: properties of water clusters and their dependence on meteorological parameters, infrared spectra, and electrical conductivity measurements of moist air. Interesting and potentially useful interpretations can be found such that water ion clusters and ion-induced neutral water clusters can account for many observations. The results suggest that these mechanisms are important in vapor-phase nucleation phenomena and therefore in cloud physics generally.
