基本解释永久雪線；陳年雪線；粒雪線词组短语短語firn -line zone 永久雪線firn line zone 永久積雪區firn line detail 萬年雪線line of firn 永久積雪線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學永久雪線粒雪線躰育萬年雪線