Laboratory and In Situ Observation of Deposition Growth of Frozen Drops

Abstract

The water vapor deposition growth of frozen drops with diameter greater than 100 mm has been studied in a thermal diffusion chamber. For varying periods of time, it was found that frozen drops experience spherical growth. The characteristic time of spherical growth depends on supersaturation, temperature, and drop size, and it varies from minutes to tens of minutes. The average rate of frozen drop growth agrees well with that predicted by the Maxwellian growth equation for ice spheres. Observations in natural clouds conducted with a cloud particle imager probe has yielded evidence that frozen drops may retain spheroidal shapes for at least 15‐20 min under conditions close to saturation over water. These observations are in agreement with the laboratory experiments. The observation of frozen drops in natural clouds may be correlated to freezing drizzle generated by overlying cloud layers that may lead to hazardous in-flight icing.