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Precipitation: What it Is and What Causes It

written by: R. Elizabeth C. Kitchen•edited by: Donna Cosmato•updated: 2/28/2011

What is precipitation? Here we will answer to this question and provide other important information about precipitation.

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    So, what is precipitation? Precipitation is defined as any type of water that comes from the sky and then falls to the earth's surface. Types of precipitation include rain, freezing rain, snow, sleet, and hail. Precipitation begins in clouds. When the water vapor droplets located within a cloud get to such a large size that the clouds' updrafts become unable to support them, the water starts to, under the force of gravity, fall to the earth. Atmospheric condensation is responsible for causing precipitation.

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    Importance of Precipitation

    The earth needs precipitation because it replenishes the earth's water. If there was no precipitation, the earth would turn into one giant desert. The duration and amount of precipitation play a role in water quality and level in estuaries. Freshwater is supplied to estuaries through precipitation, and this precipitation is a major source of nutrients and oxygen. If a drought occurs, the amount of freshwater in inland lakes and estuaries is lowered. The levels of water in a lake impact circulation patterns and drainage patterns in freshwater estuaries.

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    Measuring Precipitation

    In learning about what is precipitation, it is important to learn more about how it is measured. When measuring precipitation, it is typically done in inches or millimeters of liquid precipitation. A tipping-bucket rain gauge is one of the tools used to measure. When it fills up, it tips and then empties. There is a counter that tracks how many times it tips. To measure sleet and snow, a heated tipping-bucket rain gauge may be used. This is not the only tool used, but it is a commonly used one.

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    Causes of Precipitation

    The more water vapor present underneath a cloud and the stronger the updrafts are that result in the water vapor condensing into ice particles or cloud water, the better the chance of precipitation forming in a cloud.

    So, if there are a lot of clouds present, but no precipitation, this means that not enough water vapor is there to result in the formation of precipitation, the rising motion responsible for causing cloud formation is not strong enough, or in some cases, both. On the opposite end of the spectrum is a tropical rain shower. This is due to having a lot of available water vapor, which can produce heavy rain. This can occur, even if the cloud is small and has weak updrafts.

    When there is a warm air mass, the precipitation typically occurs with strong updrafts in localized shower clouds. With cooler air masses, the precipitation typically is associated with low pressure zones and large cloud systems.

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    BBC. (2011). What is Precipitation? Retrieved on February 26, 2011 from BBC:

    Kidzone. (2011). The Water Cycle. Retrieved on February 26, 2011 from Kidzone: