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The Atmosphere. Chapter 16 Section 1. The Water Cycle. The water cycle is a continuous movement of water from water sources, such as lakes and oceans Condensation occurs when water vapor cools and changes back into liquid droplets (cloud formation)
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The Atmosphere Chapter 16 Section 1
The Water Cycle • The water cycle is a continuous movement of water from water sources, such as lakes and oceans • Condensation occurs when water vapor cools and changes back into liquid droplets (cloud formation) • Evaporation occurs when liquid water changes into water vapor (Gas) • Transpiration is the process by which plants release water vapor into the air through their leaves • Precipitation occurs when rain, snow, sleet, or hail falls from clouds onto the Earth’s surface • Runoff is water, that flows across land into rivers, lakes and oceans
Humidity • Humidity is the amount of water vapor or moisture in the air • Relative humidity is the amount of moisture the air contains compared with the maximum amount it can hold at a particular temperature • Suppose that 1 m3 of air at a certain temperature can hold 20 g of water vapor. However, you know that the air actually contains 5 g of water vapor. What is the relative humidity?
The Process of Condensation • Condensation is the process by which a gas, such as water vapor, becomes a liquid. • Condensation occurs when the air next to a glass cools below its dew point • Dew point is the temperature to which air must cool to be completely saturated • Before water vapor can condense it must have a surface to condense on
Clouds • Clouds are a collection of millions of tiny water droplets or ice crystals • High clouds are cold do to the high altitude, high clouds are made up of ice crystals, prefix (cirro-) • Middle clouds can be made up of water droplets or ice crystals, prefix (alto-) • Low clouds are made up of water droplets, prefix (strato-) • Cumulus clouds are puffy, white clouds that tend to have flat bottoms
Clouds • Stratus clouds form in layers that cover large areas of the sky • Cirrus clouds are thin, feathery, white clouds found at high altitudes
Precipitation • Precipitation is water, in solid or liquid form, that falls from the air to the Earth • There are four major forms of precipitation rain, snow, sleet, and hail • Rain is the most common form of precipitation • Snow is the most common form of solid precipitation • Snow forms when temperatures are so cold that water vapor changes directly to a solid • Sleet, also known as freezing rain, forms when rain falls through a layer of freezing air
Precipitation • Hail is a solid precipitation that falls as balls or lumps of ice • Up drafts of air in the clouds carry raindrops to high altitudes in the cloud, where they freeze