Weather Crash Course

1. Weather Crash Course 5th Grade Science Lab

2. Water on the Earth • Water Cycle – the cycle of fresh water between Earth’s surface and the atmosphere, changing from liquid to gas to liquid • Evaporation: liquid to gas • Condensation: gas to liquid • Humidity – the amount of water vapor in the air

3. The Air Around Us • Air Pressure – the weight of the air in a given area • The higher in the atmosphere, the less pressure there is. There is less air to press down. Gravity pulls everything down…including air. So, the closer to the ground – the more air pressure there is. • Think about playing JENGA. It is easier to move the blocks at the top of the tower because there is less weight on them.

4. Warm air is less dense, or lighter, so it rises. Cool air is denser, or heavier, so it sinks. As warm air rises in the atmosphere it cools. As cool air sinks toward the ground it warms. This is a cycle. As air descends toward the ground, where pressure is high, it warms. The warming process inhibits cloud formation. As air rises into the atmosphere, where pressure is low, it cools. The cooling aids in condensation and the formation of clouds. Are you hot or cold?

5. Wind – air moving horizontally Air will naturally move where there is less pressure. When the air moves there is wind. When you squeeze a balloon you apply pressure to one end. The air inside the balloon moves to the end of the balloon where there is less pressure applied. What’s Blowing?

6. Sea Breeze During a warm day the land heats. The cool air from the ocean moves in to the land. Land Breeze During the night the land cools. The air over the land is cool. It moves out over the ocean. Feel The Breeze Water sources hold their temperature better than land. So, the temperature of land changes a lot from day to night, whereas the temperature of the water stays more stable.

7. The Winds Around the Globe • Global Winds – Earth’s rotation causes the wind to curve as it blows across its surface. • This curve is called the Coriolis Effect. • Prevailing Westerlies: blow from the west • Polar Easterlies: blow from the east • In the United States our winds blow west to east.

8. Air Masses • Polar – cold • Tropical – warm • Continental – land / dry • Maritime – water / moist • When two air masses meet they do not mix. • A boundary forms between them called a front. • Fronts often cause rainy, unsettled weather.

9. When a cold front meets a warm front the cold air moves under the warm air. This causes wind and thunderstorms. After the storm the temperatures are usually cooler because the cold front brought in cold air. When a warm front meets a cold front the warm air moves up and over the cold air. There is often precipitation that will last for days. Afterward the weather is warmer because the warm front brings in warm air. The Line that Divides

10. Causing A Spark Thunderstorms and Lightning • When intense heating causes air to rise quickly there is an updraft of wind. The rising moist air causes clouds to form. Water droplets are forming rapidly inside the cloud. When they begin to fall as rain drops it causes downdrafts. The passing updrafts and downdrafts rub against each other causing static electricity. When enough static builds up there is a spark – lightning. The heat of the lightning creates the sound of thunder.

11. What’s the weather like for you? • Climate – average weather pattern in a region, typically described using temperature and precipitation • Temperature and precipitation are affected by… • latitude: distance from the equator • bodies of water: distance from a body of water • wind patterns: easterlies or westerlies • altitude: how high above sea level a place is