2. Cirrus (mares' tails). Height (km): base=8-9, top=8-9+, ice composition, no precipitation,
process: "Head" is a small convective cell; fallstreaks of slowly evaporating snow
are distorted by upper-tropospheric wind shear.
Cirrostratus. Height (km): base=8-9, top=8-9+, ice composition,
no precipitation, process: widespread ascent.
Cirrocumulus (billow pattern). Height (km): base=8-9, top=8-9+, ice composition, no precipitation,
process: widespread ascent combined with wavelike motions in a shallow layer.