Abstract

We conduct a global assessment of the spatial heterogeneity of cloud phase within the temperature range where liquid and ice can coexist. Single-shot CALIOP lidar retrievals are used to examine cloud phase at the 333-m scale, and heterogeneity is quantified according to the frequency of switches between liquid and ice along the satellite's path. In the global mean, heterogeneity is greatest from -15 to -2C with a peak at -4C, when small patches of ice are prevalent within liquid-dominated clouds. Above -20C, heterogeneity is greatest in the northern midlatitudes and lower over the Southern Ocean, where supercooled liquid clouds dominate. Zonal mean heterogeneity undergoes an annual cycle with a peak that follows seasonal shifts in the extratropical storm track. These results can be used to improve the representation of subgrid-scale heterogeneity in general circulation models, which has the potential to reduce model biases in phase partitioning and radiation balance.