n.卷層云
Sometimes these clouds are so extensive that they are virtually indistinguishable from one another, forming a sheet of cirrus called cirrostratus. 卷云是高云的一種，是對(duì)流層中最高的云，平均高度超過(guò)6000公尺。
cirrostratus nebulosus 薄幕卷層云
cirrostratus cloud 卷層云
