1. The Atmosphere Chapter 16 Section 1

2. 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 Water Cycle Quiz

3. 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 m 3 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?

4. 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

5. 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

6. Clouds Stratus clouds form in layers that cover large areas of the sky Cirrus clouds are thin, feathery, white clouds found at high altitudes

7. 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

8. 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