How do we measure Weather?

What’s the Weather Like? Unit 3 Lesson 3 How Do We Measure Weather? What’s the Weather Like? Weather is what the atmosphere is like at a given time and place. Meteorologists are scientists who study weather. Factors such as air temperature, amount of cloud cover, and amount of precipitation are used to create weather reports. Copyright © Houghton Mifflin Harcourt Publishing Company 2

What’s the Weather Like? Unit 3 Lesson 3 How Do We Measure Weather? What’s the Weather Like? Weather reports can help you plan your day. Airports use weather reports to plan flight schedules. Farmers use weather reports to help care for their crops. Copyright © Houghton Mifflin Harcourt Publishing Company 3

Unit 3 Lesson 3 How Do We Measure Weather? Watching the Weather Weather balloons are used to carry weather tools high into the atmosphere. A wind vane measures wind direction by pointing in the direction from which the wind blows. An anemometer measures wind speed. Wind speed is measured in kilometers per hour. Copyright © Houghton Mifflin Harcourt Publishing Company 4

Watching the Weather A barometer measures air pressure. Unit 3 Lesson 3 How Do We Measure Weather? Watching the Weather A barometer measures air pressure. A hygrometer measures the amount of water vapor, or humidity, in the air. Relative humidity is a percentage. It tells the amount of water vapor in the air compared to what the air can hold at a given temperature. Copyright © Houghton Mifflin Harcourt Publishing Company 5

Lying Low, Reaching High Unit 3 Lesson 3 How Do We Measure Weather? Lying Low, Reaching High Shape and height are used to classify clouds. Stratus clouds form flat layers that cover most of the sky. Cirrus clouds are thin, white, and feathery. Cumulus clouds are puffy and white. Copyright © Houghton Mifflin Harcourt Publishing Company 6

Lying Low, Reaching High Unit 3 Lesson 3 How Do We Measure Weather? Lying Low, Reaching High Low clouds form below about 2,000 m (6,500 ft). Middle clouds form between 2,000 m and 6,000 m (6,500 ft and 20,000 ft). High clouds form above 6,000 m (20,000 ft). High clouds are often made of ice crystals because of the low temperatures. Copyright © Houghton Mifflin Harcourt Publishing Company 7

Lying Low, Reaching High Unit 3 Lesson 3 How Do We Measure Weather? Lying Low, Reaching High Use this cloud classification chart to identify the clouds in the sky today. Copyright © Houghton Mifflin Harcourt Publishing Company 8

It’s Pouring Solids and Liquids Unit 3 Lesson 3 How Do We Measure Weather? It’s Pouring Solids and Liquids Precipitation is solid or liquid water that falls from clouds to Earth’s surface. As air temperature changes, precipitation may fall as either a solid or liquid. Air temperature changes by season, elevation, and location. Copyright © Houghton Mifflin Harcourt Publishing Company 9

It’s Pouring Solids and Liquids Unit 3 Lesson 3 How Do We Measure Weather? It’s Pouring Solids and Liquids Rain is liquid and falls through warm or cool air. Snow is solid and falls through cold air. Sleet is precipitation that freezes near the ground. Hail is solid precipitation made of layers of ice. Copyright © Houghton Mifflin Harcourt Publishing Company 10

Rain Rain can start out high in the atmosphere as snow. Unit 3 Lesson 3 How Do We Measure Weather? Rain Rain can start out high in the atmosphere as snow. Raindrops can range in size from about 0.1 mm in diameter to as large as 6 mm in diameter. Rain gauges are used to measure the depth of rain that falls in an area. Copyright © Houghton Mifflin Harcourt Publishing Company 11

Sleet Sleet is made up of small pellets of ice. Unit 3 Lesson 3 How Do We Measure Weather? Sleet Sleet is made up of small pellets of ice. Sleet can form when snow partially melts as it falls through a warm layer of air. The melted snow can freeze again in a cold layer near the ground to form sleet. Copyright © Houghton Mifflin Harcourt Publishing Company 12

Unit 3 Lesson 3 How Do We Measure Weather? Hail Hail forms when wind carries raindrops high into the colder part of a cloud. The raindrops freeze and fall to a warmer part of a cloud. A new layer of moisture may stick to the hail particles. Copyright © Houghton Mifflin Harcourt Publishing Company 13

Hail The wind can carry the hail particles up again and again. Unit 3 Lesson 3 How Do We Measure Weather? Hail The wind can carry the hail particles up again and again. Large hail particles will fall to the ground. Copyright © Houghton Mifflin Harcourt Publishing Company 14

Unit 3 Lesson 3 How Do We Measure Weather? Snow Snow forms when water vapor turns directly into a solid in the atmosphere. Air currents keep snow crystals in the atmosphere. Once a snow crystal is too large, it will fall to Earth. Copyright © Houghton Mifflin Harcourt Publishing Company 15