Especially in autumn and winter when the air is not so unstable, cumulus clouds may merge and cover a large part of the sky. They become altocumulus.是什么意思_Especially in autumn and winter when the air is not so unstable, cumulus clouds may merge and cover a large part of the sky. They become altocumulus.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句