Download Unit C Chapter 1 - St. Ursula School

Science Unit C: Chapter 1 - Measuring Weather study guide
Lesson 1: How Does Sunlight Affect Air Temperature?
1. At noon, the sun hits the earth at the most direct angle.
2. The sun hits the earth less directly in the morning and in the evening.
3. Temperatures are usually lowest before sunrise. The earth’s surface is usually warmest around midday, but it
takes time for the surface to heat the air. This means air temperatures are highest in the middle of the
afternoon.
4. summer – warmer because of longer daylight hours
5. Different surfaces absorb different amounts of light energy. Blacktop, cement, and buildings heat up more
quickly than water or grass, therefore the air above or around these surfaces will heat up more.
6. thermometer - tool used to measure temperature in degrees
Liquid in the thermometer heats up, which makes it expand (spread out).
Lesson 2: How Does Temperature Affect Air Movement?
1. air pressure - the amount that air presses or pushes on anything
a. Lower air pressure can be felt high above the earth.
b. In an airplane, your eardrums can feel the change in pressure.
2. Air is cooler when it is further from the earth’s surface.
3. low- pressure area – where warm air rises and pushes down on the earth’s surface with less pressure
4. high-pressure area – where cool air sinks and pushes down on the earth’s surface with more pressure
5. Wind blows from an area of high pressure (cooler air sinks) to an area of low pressure (warmer air rises).
6. barometer - a tool filled with mercury that measures air pressure
7. wind vane - a tool that shows wind direction
8. anemometer - a tool that measures wind speed
Lesson 3: What Causes Clouds and Precipitation?
1. cloud formation
a. warm air rises and carries water vapor
b. as it cools, it condenses into drops
c. many drops together form clouds
2. location of clouds
a. many clouds in areas with moist air
b. few clouds in areas with dry air (deserts)
3. fog – a cloud that forms close to the ground
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Sc. Unit C: Ch. 1 – guide cont.
4. types of clouds
a. stratus
(1) low in the sky
(2) form flat, wide layers
(3) rain or snow may fall
b. cumulus - white, fluffy like cotton
(1) high in the sky
(2) dome shaped with flat bottoms
(3) warm moist air
(4) seen during fair weather
c. cirrus
(1) high in the sky where it is cold
(2) mostly ice crystals
(3) look like thin threads or feathers
(4) usually mean warm weather
5. precipitation - moisture that falls from clouds to the ground
a. rain – when the air temperature near the earth is above freezing
b. snow – when the air temperature near the earth is below freezing
c. hail - rain that freezes and is pushed higher in the air by strong winds
6. rain gauge - a tool that measures precipitation
7. humidity - the amount of water vapor in the air
8. hygrometer - a tool that measures humidity
9. water cycle – water from the earth evaporates, condenses, and falls as precipitation
Lesson 4: How Do Meteorologists Predict Weather?
1. air mass
a. large body of air that has the same temperature and humidity
b. differences in air pressure and wind can cause them to move (usually from west to east in the U.S.)
c. air masses do not mix
2. front
a. the line where two air masses meet
b. cold mass pushes into a warm mass
(1) warm air rises quickly and cools rapidly
(2) causes huge storms (snow or rain), but may not last long because cold fronts move quickly
c. warm mass meeting a cold mass
(1) warm mass slides slowly up over cold mass
(2) warm mass rises , cools, forms clouds
(3) cause gentle rain or snow, may last several days, mild weather follows
3. forecast – a prediction of what the weather will be like
4. meteorologist - a person who studies weather
5. National Weather Service
a. government agency that collects weather information
b. use radar, satellites, and weather balloons to collect information instantly all around the world
6. safety
a. a watch – severe weather may be coming, get prepared
b. a warning – severe weather has been seen in your area, take shelter
c. thunderstorm – take shelter in a car or inside; lightning strikes trees, stay out of water, don’t use
telephone or electrical appliances
d. flash flood – stay away from fast moving water; roads, cars, houses, etc. can be washed away
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