卷层云（Cs）（拉丁学名Cirrostratus）白色透明均匀的云雾，地物有影，日月轮廓分明，常伴有晕。

一般可分为两种云状：

Cirrostratus /ˌsɪroʊˈstrɑːtəs/ is a high, very thin, generally uniform stratiform genus-type of cloud, composed of ice-crystals. It is difficult to detect and is capable of forming halos when the cloud takes the form of thin cirrostratus nebulosus. The cloud has a fibrous texture with no halos if it is thicker cirrostratus fibratus. On the approach of a frontal system, the cirrostratus often begins as nebulosus and turns to fibratus. If the cirrostratus begins as fragmented fibratus it often means the front is weak. Cirrostratus is usually located above 5.5 km (18,000 ft). Its presence indicates a large amount of moisture in the upper atmosphere.