Field measurements of submicron aerosol washout by snow

Abstract

Direct field measurements of the washout of submicron aerosols by snow have been accomplished by high‐speed sampling of the atmospheric aerosol spectrum and of the rate of snowfall. For the aerosol size range 0.29 µm ≤ D ≤ 1.48 µm, the values of the measured washout coefficients are 4.82×10 −4 ≤ λ S ≤ 6.35×10 −3 sec −1 , and show no systematic dependence on aerosol diameter. Comparison of the results with those previously derived for rain washout indicate that snow scavenging is ∼28–50 times more efficient per equivalent water content. Average aerosol lifetimes due to washout by snowfall are of the order of 0.7 hours, thus establishing snow scavenging as the dominant aerosol sink in regions having significant snowfall during the winter season.