Unit 11 Lesson 2 Elements of Weather Copyright © Houghton Mifflin Harcourt Publishing Company 1

Unit 11 Lesson 2 Elements of Weather Florida Benchmarks SC.6.E.7.2 Investigate and apply how the cycling of water between the atmosphere and hydrosphere has an effect on weather patterns and climate. SC.6.E.7.3 Describe how global patterns such as the jet stream and ocean currents influence local weather in measureable terms such as temperature, air pressure, wind direction and speed, and humidity and precipitation. Copyright © Houghton Mifflin Harcourt Publishing Company 2

Wonder About Weather? What is weather? Unit 11 Lesson 2 Elements of Weather Wonder About Weather? What is weather? Weather is the condition of Earth’s atmosphere at a certain time and place. Weather conditions in the atmosphere can be recognized through direct observation. Copyright © Houghton Mifflin Harcourt Publishing Company 3

What is temperature and how is it measured? Unit 11 Lesson 2 Elements of Weather What is temperature and how is it measured? Temperature is how hot or cold something is. Thermometers are used to measure temperature. Some thermometers use the thermal expansion of a liquid to determine temperature. Electrical thermometers use the strength of an electric current to determine temperature. Copyright © Houghton Mifflin Harcourt Publishing Company 4

What is humidity and how is it measured? Unit 11 Lesson 2 Elements of Weather What is humidity and how is it measured? Humidity is the amount of water vapor in the air. As more water evaporates, humidity increases. Relative humidity is the amount of water vapor in the air compared to the amount of water vapor needed to reach saturation. Air is saturated when the rates of evaporation and condensation are equal. Copyright © Houghton Mifflin Harcourt Publishing Company 5

What is humidity and how is it measured? Unit 11 Lesson 2 Elements of Weather What is humidity and how is it measured? Dew point is the temperature at which more condensation than evaporation occurs. When air temperature drops below the dew point, condensation forms dew, fog, and clouds. Copyright © Houghton Mifflin Harcourt Publishing Company 6

What is precipitation and how is it measured? Unit 11 Lesson 2 Elements of Weather What is precipitation and how is it measured? Precipitation is any form of water that falls to Earth’s surface from the clouds, including rain, snow, hail, and sleet. Rain forms as water condenses. Copyright © Houghton Mifflin Harcourt Publishing Company 7

What is precipitation and how is it measured? Unit 11 Lesson 2 Elements of Weather What is precipitation and how is it measured? Snow forms when temperatures are low enough to turn water vapor into a solid. Hailstones are layered lumps of ice formed during severe thunderstorms. Copyright © Houghton Mifflin Harcourt Publishing Company 8

The Air Out There What is air pressure and how is it measured? Unit 11 Lesson 2 Elements of Weather The Air Out There What is air pressure and how is it measured? Air pressure is the force of air molecules pushing on an area. A barometer is used to measure air pressure. Air pressure and density decrease with altitude. Copyright © Houghton Mifflin Harcourt Publishing Company 9

What is wind and how is it measured? Unit 11 Lesson 2 Elements of Weather What is wind and how is it measured? Wind is air that moves horizontally, or parallel to the ground. Wind is a result from differences in air pressure. Over a short distance, air moves from higher pressure to lower pressure. An anemometer is used to measure wind speed. A wind vane or wind sock is used to measure wind direction. Copyright © Houghton Mifflin Harcourt Publishing Company 10

What is visibility and how is it measured? Unit 11 Lesson 2 Elements of Weather What is visibility and how is it measured? Visibility is a measure of the distance at which an object or light can be clearly seen. Visibility is measured by using three to four known landmarks at different distances. Air pollution or fog can cause poor visibility. Copyright © Houghton Mifflin Harcourt Publishing Company 11

What are some ways to collect weather data? Unit 11 Lesson 2 Elements of Weather What are some ways to collect weather data? Weather data can be collected at ground stations, by weather buoys, by ships, by airplanes, and by satellites. Copyright © Houghton Mifflin Harcourt Publishing Company 12