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Precipitation Nicole Lavigne 11/30/07 T-3 Vocabulary • Precipitation: is any form of water that falls from clouds and reaches earth’s surface. • Rain gauge: is an open-ended can or tube that collects rainfall. • Droughts: can cause great hardship • Common types of precipitation include rain, sleet, freezing rain, hail, and snow: In warm parts of the world, precipitation is almost always rain or drizzle. In colder regions, precipitation may fall as snow or ice. • Rain is measured with a rain gauge- The amount of rain fall is measured by dipping a ruler into the water or by reading a marked scale. • Scientists have used cloud seeding to produce rain and to clear fog from airports- Dry ice is sprinkled into the fog, causing ice crystals to form. This removes some of the fog so pilots can see the runway. Unfortunately, cloud seeding clears only cold fog, so it’s used for this purpose is limited. A rain gauge Five common types of rain • • • • • Rain: the most common kind of precipitation is rain. Sleet: sometimes raindrops fall though a layer of air below 0c, the freezing point of water. Freezing Rain: at other times raindrops falling though cold air near the ground do not freeze in the air. Hail: round pellets of ice larger than 5 millimeters in diameter are called hailstones. Hail forms only inside cumulonimbus clouds during thunder storms. A hail stone starts as an ice pellet inside a cold region of a cloud. Snow: often water vapor in a cloud is converted cloud directly into ice crystals called snowflakes. Measuring/ controlling precipitation • Measuring precipitation: meteorologists measure rainfall with a rain gauge. A rain gauge is an openended can or tube that collects rainfall. • Controlling precipitation: In some regions there maybe periods that are much drier than usual. Long period of unusually low precipitation are called droughts can cause grant hard ship. How do hail storms form? • Hail only forms inside cumulonimbus clouds during thunder storms.