n.卷层云
Sometimes these clouds are so extensive that they are virtually indistinguishable from one another, forming a sheet of cirrus called cirrostratus. 卷云是高云的一种，是对流层中最高的云，平均高度超过6000公尺。
cirrostratus nebulosus 薄幕卷层云
cirrostratus cloud 卷层云
