1. What is Weather?
Weather is the conditions of Earth’s atmosphere at a certain time and place.
For example, sunshine, rain, hurricanes, and storms are all examples of weather.
Weather is different at different places around the world.
© Erin Kathryn 2016

2. Earth’s Atmosphere
The atmosphere is the layers of air that surround Earth’s surface.
Earth’s atmosphere has 4 layers: troposphere, stratosphere, mesosphere and thermosphere.
Weather occurs in the first layer of the atmosphere, the troposphere.
© Erin Kathryn 2016

3. The Water Cycle
The water cycle is the movement of water into the air as water vapor and back to Earth’s surface as precipitation.
The water on Earth is
constantly changing
from one form to
another in a continuous
cycle that occurs over
and over again.
© Erin Kathryn 2016

4. The Water Cycle
Evaporation - Water evaporates (changes from a liquid to a gas) into water vapor due to heat from the Sun.
Condensation – Water condenses (changes from a gas into a liquid) into water droplets. These water droplets form clouds.
© Erin Kathryn 2016

5. Types of Clouds
Different types of clouds bring various types of weather.
Cloud
Description
Picture
stratus
Low-level cloud that forms in layers and usually brings rain
cumulus
Fluffy clouds that are flat on the bottom and usually mean fair weather
cirrus
Thin clouds that look like feathers and form high in the sky; usually bring fair weather
cumulonimbus
Tall clouds that bring thunderstorms
© Erin Kathryn 2016

6. Types of Clouds
Different types of clouds bring various types of weather.
Cloud
Description
Picture
fog
Cloud that forms close to the ground
altocumulus
Small, white, puffy, middle level cloud
stratocumulus
Low puffy, gray clouds that can sometimes produce rain
cirrocumulus
High clouds that look like tiny cotton balls bunched together
altostratus
Dark gray covering cloud that usually brings rain
© Erin Kathryn 2016

7. The Water Cycle
Precipitation- When clouds become too heavy, the water droplets fall to Earth’s surface in the form of rain, snow, sleet, or hail.
Collection– Precipitation collects in rivers, streams, oceans, and lakes allowing it to be evaporated and begin the water cycle again.
© Erin Kathryn 2016

8. Types of Precipitation
rain
Falling drops of liquid water
snow
Falls when the temperature in the cloud is below freezing (32°F)
sleet
Rain that freezes as it falls to Earth’s surface
hail
Forms when drops of rain freeze in the cloud and are carried higher into the cloud freezing over and over before falling to Earth’s surface
© Erin Kathryn 2016

9. The Water Cycle
Runoff- Precipitation that flows downhill on Earth’s surface to rivers, streams, lakes, and oceans is called runoff.
Infiltration– Some precipitation soaks into the ground. This is called infiltration or groundwater.
© Erin Kathryn 2016

10. What Causes Weather?
Weather conditions include temperature, humidity, wind, and air pressure.
Temperature – how hot or cold the air is
Humidity – the amount of water vapor in the air
Wind – the movement of air
Air pressure – the weight of air as it presses down on Earth.
© Erin Kathryn 2016

11. Weather Instruments
Weather conditions can be measured using various weather instruments.
thermometer
rain gauge
Measures the temperature of the air
Collects and measures the amount of precipitation that has fallen in an area
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12. Weather Instruments
Weather conditions can be measured using various weather instruments.
barometer
anemometer
Wind vane
Measures air pressure
Measures the speed of the wind
Measures the direction of the wind
© Erin Kathryn 2016

13. Air Masses
An air mass is a large body of air that has about the same temperature, air pressure, and moisture.
Air masses are either warm or cold and either moist or dry.
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14. Air Masses Warm air masses usually form near warm places.
Cold air masses usually form near cold places.
Moist air masses usually form over oceans.
Dry air masses usually form over land.
Most changes in weather happen when one air mass moves into a place and pushes out another air mass.
© Erin Kathryn 2016

15. Weather Patterns & Fronts
The place where two air masses meet is called a front.
Weather can change suddenly when a front moves across an area.
Many storms and precipitation take place along fronts.
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16. Cold Front
When a cold air mass meets a warm air mass a cold front forms.
The cold air moves under the warm air, pushing it up.
The warm air rises, clouds and precipitation occur.
Cold fronts often bring thunderstorms.
Cold front symbol on a weather map 
© Erin Kathryn 2016

17. Warm Front
A warm front forms when a warm air mass pushes into a cold air mass.
The warm air slowly moves up and over the cold air forming layers of gray clouds and steady precipitation.
Warm front symbol on a weather map 
© Erin Kathryn 2016

18. Meteorology Meteorology is the study of weather.
This involves the measuring of conditions near Earth’s surface and high in the atmosphere.
Meteorologists identify air masses and fronts.
They also predict where they will move.
© Erin Kathryn 2016

19. Weather Maps
These predictions help meteorologists create a weather map.
Weather maps are used to help forecast the weather.
Weather maps use symbols to show the location of fronts and precipitation.
A forecast is a prediction of what the weather will be for a certain day, week, or longer period of time.
© Erin Kathryn 2016

20. Severe Weather
Severe weather includes hurricanes, tornadoes, and snowstorms.
Meteorologists study and forecast storms using various tools.
Forecasters can give weather warnings when severe weather is likely to move into an area.
Warning give people time to prepare or leave an area.
© Erin Kathryn 2016

21. Climate
Climate is the usual weather conditions of a place over an extended amount of time.
Climate has a lot to do with the kinds of plants and animals that can live and survive there.
© Erin Kathryn 2016

22. Climate
How much sunlight an area gets, oceans or large bodies of water, altitude, and mountains are all factors that affect climate.
Scientists learn about climate by looking at tree rings in old fossils and evaluating core samples of ice to see how the layers of fossil and ice have changed over time.
© Erin Kathryn 2016