Editing Altostratus cloud (section)

=== Microphysical properties ===
Altostratus can be composed of water droplets, [[supercooled]] water droplets, and ice crystals,<ref name="Cloud-Classification" /> but ice crystals make up the vast majority.<ref>{{harvnb|Sassen|Wang|2012|pp=679–680}}</ref> In some altostratus clouds made of ice crystals, very thin horizontal sheets of water droplets can appear seemingly at random, but they quickly disappear.<ref name="platt-344">{{harvnb|Platt|1977|p=344}}</ref> The sizes of the ice crystals in the cloud tended to increase as altitude decreased. However, close to the bottom of the cloud, the particles decreased in size again. During the sampling of one cloud, the scientists noted a [[Halo (optical phenomenon)|halo]] while flying near the top of the cloud, which indicated that the ice crystals were hexagonal near the top. However, farther down, the ice crystals became more conglomerated.<ref name="field-1929">{{harvnb|Field|1999|p=1929}}</ref><ref name="field-1933">{{harvnb|Field|1999|p=1933}}</ref> Mixed-phase (containing both ice and water) altostratus clouds contain a "melt layer", below which the ice crystals tend to melt into water droplets. These water droplets are spheres and thus fall much faster than ice crystals, collecting at the bottom of the cloud.<ref name="Danne-182">{{harvnb|Danne|Quante|Milferstädt|Lemke|1999|p=182}}</ref>