基本解释永久雪线；陈年雪线；粒雪线词组短语短语firn -line zone 永久雪线firn line zone 永久积雪区firn line detail 万年雪线line of firn 永久积雪线firn line更多词组英英字典柯林斯英英字典 the zone of a glacier between the lower region of solid ice and the upper region of nv, above which ablation occurs (Also called firn limit)firn line剑桥字典firn line柯林斯字典专业释义地球科学永久雪线粒雪线体育万年雪线