if there is snow on the runways they are plowed and sweepers are towed behind the plow truck. the object is to keep the surface as "dry as possible". Urea is only used if there is freezing precipitation because using it on snow causes slush and standing water to form on the surface which degrades A/C T/O performance. The term "de-ice refers to spraying hot water to melt ice and the term anti-ice refers to applying glycol.