Evaluating the cloud droplet number from particle size distribution measurements: A comparison of evaluated and measured cloud droplet number concentrations

While a large number of field investigations on aerosol CCN activity and cloud microphysics have been performed, very little information on the activation characteristics of the smallest aerosol particles (those close to or below 0.1 μm in diameter) is available. Here we approach the problem in a slightly different way to traditional methods by measuring simultaneously the cloud interstitial particle size spectrum and nearby out-of-the cloud particle size spectrum. The main advantage of this approach is that one can determine the activated fraction of different-size particles over the whole submicron size range (Komppula et al., 2005). This paper presents a comparison of the cloud droplet number evaluated from particle size distributions and the measured cloud droplet number.