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| Title: |
THICKNESS OF COLD AIR DETERMINES TYPE OF PRECIPITATION |
| Caption: |
In winter storms, the thickness of cold air at the surface determines the type of precipitation. (a) Most precipitation begins falling as snowflakes and remains as snow if it does not pass through warm air before reaching the ground. (b) Falling snowflakes melt if they encounter warm air aloft, and the resulting rain refreezes to form ice pellets (sleet) if there is sufficient time and cold air before they reach the ground. (c) If there is only a thin layer of cold air at the surface, raindrops become supercooled and then freeze immediately upon contact with a cold surface such as a tree limb, house, or power line. (d) Snowflakes will melt and rain will fall if a thick warm air layer is at the surface. (After Linda Scott/Austin American-Statesman) |
| Keywords: |
atmosphere, midlatitude cyclones, middle-latitude cyclones, precipitation, snow, rain, sleet |
