Measurement of Growth Rate to Determine Condensation Coefficients for Water Drops Grown on Natural Cloud Nuclei

Growth rate measurements were made for water drops grown on nuclei in atmospheric air samples taken in Rolla, Missouri. Rolla, having a population of 15,000 and very little industry, is relatively free of urban pollutants. The measurements were made in a vertical flow thermal diffusion chamber at supersaturations of 0. 5 and 1%. The time to grow from near dry radius to the final radius (6 to 7. 5 mu m) was measured. If one assumes the thermal accomodation coefficient is unity, the measurements indicate an average value of 0. 026 for the condensation coefficient. The temperature ranged from 22. 5 to 25. 7 degree C