cloud的形容词形式是什么？

　　例句：

　　The plane disappeared behind a cloud.

　　飞机消失在云层里。

　　"Cloud Street" is already in its third printing.

　　《云街》已经是第3次印刷了。

　　Fog and low cloud cover are expected this afternoon.

　　预计今天下午有雾和低空云层。