Laser heterodyne study of water droplet growth

Droplet growth by condensation under simulated atmospheric conditions has been studied quantitatively in a diffusion cloud chamber. Droplet size distributions were obtained from heterodyne spectra of scattered laser light. The distributions were typically quite narrow, and the time dependence of the mean radius agrees well with theoretical predictions for supersaturations of 1.02–1.05 in the size range 3–7 μm. Our data indicate no need to postulate very small condensation and thermal accommodation coefficients in contrast to previously published work at higher supersaturations. However, the growth rates are anomalously low at supersaturations less than about 1.015.