Mechanisms of transport from the atmosphere to the Earth's surface

Wind-tunnel experiments have been made with wind speeds of 3 through 8 m/sec, and deposition on a water surface has been studied. The deposition velocity νg was measured for water vapor, carbon dioxide, atomic lead, purified-water residual nuclei, sodium chloride aerosols, and polystyrene latex spheres. Radioactive tracers were used for detection. The studies covered diffusion coefficients D from nearly 10−7 to 0.25 cm2/sec, and all were carried out under the same conditions. The results are best fitted by a relation ν ∝ D2/3 in the range 2×10−2 ≥ D ≥ 2×10−5 cm2/sec and thus favor the concept of proportionality between the characteristic length in the turbulent boundary layer and the height above the surface.