How does riming influence the observed spatial variability of ice water in mixed-phase clouds?

Abstract

Observations show that the ice water content (IWC) in mixed-phase clouds (MPCs) tends to occur in clusters. However, it is not sufficiently understood which ice crystal formation and growth processes play a dominant role in IWC clustering in clouds. One important ice growth process is riming, which occurs when liquid water droplets freeze onto ice crystals upon contact. Here we use airborne measurements of MPCs at mid- and high-latitudes to investigate the spatial variability of ice clusters in clouds and how this variability is linked to riming. We use data from the IMPACTS (mid-latitudes) and the HALO-(AC)3 (high-latitudes) aircraft campaigns, where spatially and temporally colocated cloud radar and in situ measurements were collected. We derive riming and IWC by combining cloud radar and in situ measurements. Ice cluster scales in clouds are quantified using pair correlation functions.