Cloud Microphysical Structure Analysis Based on High-Resolution In Situ Measurements

Abstract

This study investigates the microphysical parameters and shapes of droplet size distributions (DSDs) along three aircraft traverses of developing convective clouds during Cloud Aerosol Interactions and Precipitation Enhancement Experiment (CAIPEEX) Phase III 2015 at a sampling frequency of 25 Hz. The droplet number concentration (Nc, cm23), and liquid water content (LWC, g m23) present steep gradients within zones of a few tens of meters near the cloud edges and relatively gentle gradients in the strong updraft zones. Sometimes, the horizontal LWC distribution resembles a trapezoidal shape with steep LWC and Nc gradients near the cloud edges. The LWC maximums (LWCmax) are lower than the adiabatic LWCs, but the high adiabatic fractions in the cloud core indicate low dilution. High LWC/LWCmax, largest droplets, and narrow and similarly shaped DSDs are found in the regions of high updrafts. Zones of low LWC/LWCmax are found close to the cloud edges, where DSDs are highly diverse, containing both large and small droplets. Finally, we analyze the mixing diagrams. Significant in-phase turbulent fluctuations in LWC and Nc were found. The effective radii change slightly across cloud updraft zones but decrease at the zone of low LWC/LWCmax ratio close to cloud edges. The spectra of LWC and Nc obey Kolmogorov 25/3 turbulence law. The radii of the correlation of LWC and Nc in updraft zones are of several tens of meters. Filaments up to 120–175 m in size are also noticed.