unit 3 lesson

8/10/2019 Unit 3 Lesson

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Unit 3 Lesson 3 How Do We Measure Weather?

Copyright Houghton Mifflin Harcourt Publishing Company


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Unit 3Lesson 3 How Do We Measure Weather?

Whats the Weather Like?


Weatheris what the atmosphere is like at a giventime and place.

Meteorologists are scientists who study weather.

Factors such as air temperature, amount of cloudcover, and amount of precipitation are used tocreate weather reports.


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Whats 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 theircrops.


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Watching the Weather


Weather balloons are used to carry weather toolshigh into the atmosphere.

Awind vane

measures wind direction by pointingin the direction from which the wind blows.

An anemometermeasures wind speed. Windspeed is measured in kilometers per hour.


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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). Highclouds are often made of ice crystals because ofthe low temperatures.


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Lying Low, Reaching High


Use this cloud classification chart to identify theclouds in the sky today.


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Its Pouring Solids and Liquids


Precipitationis solid or liquid water that falls fromclouds to Earths surface.

As air temperature changes, precipitation may fallas either a solid or liquid.

Air temperature changes by season, elevation,and location.


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Its 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.


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Rain

Rain can start out high in the atmosphere assnow.

Raindrops can range in size from about 0.1 mm indiameter to as large as 6 mm in diameter.

Rain gauges are used to measure the depth ofrain that falls in an area.




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Sleet

Sleet is made up of small pellets of ice.

Sleet can form when snow partially melts as itfalls through a warm layer of air.

The melted snow can freeze again in a cold layernear the ground to form sleet.




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Hail

Hail forms when wind carries raindrops high intothe colder part of a cloud.

The raindrops freeze and fall to a warmer part of acloud.

A new layer of moisture may stick to the hailparticles.




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Hail

The wind can carry the hail particles up again andagain.

Large hail particles will fall to the ground.




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Snow

Snow forms when water vapor turns directly into asolid in the atmosphere.

Air currents keep snow crystals in theatmosphere.

Once a snow crystal is too large, it will fall toEarth.



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