On the Cluster Scales of Hydrometeors in Mixed-Phase Stratiform Clouds

Mixed-phase stratiform clouds contain numerous liquid, mixed-phase, and ice clusters, quantifying the cluster scales is potentially helpful to improve the parameterizations of microphysics and radiation models. However, the scales of hydrometeor clusters at different levels of stratiform clouds are not well understood. In this study, using airborne measurements and a large eddy simulation, we show that turbulence plays an important role in controlling the clusters with length of a few hundred meters, while the scales of larger clusters have stronger vertical variations from cloud base to top. The liquid clusters are the largest near the cloud top, while the lengths of ice clusters decrease from cloud base to top. The lengths of mixed-phase clusters depend on the glaciation process, a faster glaciation results in smaller mixed-phase clusters. The results improve our understanding on how the liquid and ice are mixed at different levels in stratiform clouds. Mixed-phase clouds are vital to the global radiative balance and water cycle. The coexistence of liquid and ice, and the way they mix have significant impacts on the cloud microphysical properties. Observations suggest hydrometeors organize in clusters in mixed-phase stratiform clouds, while such inhomogeneity is still poorly represented in models. In this study, using airborne measurements and model simulation, we analyzed the scales of liquid, mixed-phase, and ice clusters at different levels in a stratiform cloud observed in Northeast China. The results suggest turbulence controls the scale of clusters with length of a few hundred meters, while larger clusters have stronger vertical variations. The results improve our understanding on the cluster scales of hydrometeors at different levels in stratiform clouds, and are potentially helpful to improve the parameterizations of microphysics and radiation. Turbulence plays an important role in controlling the scale of hydrometeor clusters The scales of liquid, mixed-phase, and ice clusters have different height dependencies from cloud top to base A faster glaciation process results in smaller mixed-phase clusters