Relative dispersion of ice crystals in seeded cumuli

Abstract

A quasi-instantaneous, vertical area source of ice was generated by releasing dry-ice pellets from an airplane. The ice concentration distribution and relative dispersion were measured normal to the source and were complemented by cloud turbulence measurements, namely, velocity variances and the energy dissipation rate ε. The clouds were selected based on an objective set of criteria and were treated as members of the same ensemble. The observed mean relative dispersion agreed well with predictions from a Lagrangian stochastic two-particle model, which reproduces Batchelor's theoretical results. In addition to the mean dispersion, probability density functions of the individual dispersion observations were constructed and showed an evolution from a highly skewed pdf at small times to a more symmetrical one at large times. -from Authors