Weather Study Guide

Name: ______Date: ______

Weather Study Guide

Water:

Water can be a solid, liquid, or a gas.
Water can change from one of these forms to another.
Matter is anything that takes up space and has weight.
Matter exists in different physical forms, called states.
A solid is matter that keeps its own shape.
A liquid is matter that takes the shape of its container.
A gas is matter that spreads out in all directions.
Water in its gas state is called water vapor.
Melting is the change of matter from a solid to a liquid.
Temperature is a measure of how much heat energy an object has.
Evaporation is the change of matter from a liquid to a gas.
Water begins to boil at 100 degrees Celsius.
When water heats up, its particles start to move faster and they move farther apart.
Condensation is the change of matter from a gas to a liquid.
Freezing is the change of matter from a liquid to a solid.
When water gets colder, its particles move more slowly.
Water freezes at 0 degrees Celsius.

Clouds & Precipitation:

Clouds are masses of tiny water droplets or ice crystals.
Clouds form when water vapor in the air condenses.
The atmosphere is the blanket of gases that surrounds Earth.
Weather is the condition of the atmosphere at a certain time and place.
Stratus clouds are low sheets of gray clouds.
They spread out and look like a gray blanket covering the sky.
Some stratus clouds bring rain.
Cumulus clouds are usually puffy and white.
You see them in nice weather.
They are usually higher in the sky than stratus clouds.
They are often spread out, with big space of blue sky between them.
Sometimes cumulus clouds are dark.
These dark clouds bring rain, lightning, and thunder.
The highest clouds are cirrus clouds.
They are wispy and look a little like feathers in the sky.
They form where the air is very cold.
They are made up of ice crystals.
You see these thin clouds in fair weather, but rainy weather oftenfollows in a day or two.
Fog is a cloud that is on or near the ground.
Precipitation is water that falls from the atmosphere.
The water can take the form of rain, snow, sleet, or hail.
Rain falls in drops.
Some raindrops form when droplets bump into each other and stick together.
It takes millions of droplets to make one raindrop.
Snow falls from cold clouds when ice crystals stay frozen as they fall.
The falling ice crystals stick together to form snowflakes of different sizes.
Depending on the temperature, snow may be light and powdery orheavy and wet.
Sleetis frozen or partly frozen rain.
Sleet forms when raindrops fall through very cold air near the ground.
Hail is precipitation in the form of balls or chunks of ice.
Dark cumulus clouds often produce hail.
Hailstones start as tiny pellets of ice inside these clouds.
Most hailstones are small, but some are as big as softballs.

The Water Cycle:

The water cycle is the movement of water between Earth’s surface and atmosphere.
Water moves from the oceans and land into the air and back again.
A cycle is a set of events that happen over and over.
It does not have a beginning or an end.

The water cycle has four main steps.
Step 1
The sun warms liquid water on Earth’s surface in oceans and lakes.
The sun’s energy makes some of the liquid water change to a gas.
This change from a liquid to a gas is called evaporation.
The water vapor rises into the air.
It moves from Earth’s surface into the atmosphere.
Step 2
As water vapor rises, it cools off.
When it gets cool enough, the water vapor changes back to liquidwater.
This change from a gas to a liquid is called condensation.
The water vapor condenses into tiny droplets of liquid water.
These droplets form clouds.
Step 3
Droplets of liquid water in clouds combine with other droplets and grow.
When they become too big and heavy, they fall to Earth’s surface as precipitation.
Step 4
Some precipitation falls into the oceans.
Some falls on land.
Some of it flows downhill over the ground.
Water that flows over the ground is called runoff.
The runoff flows into bodies of water, such as rivers, lakes, and oceans.
There, evaporation keeps the water cycle going.

Measuring Weather:

A meteorologist is a scientist who studies weather.
Meteorologists use thermometers to measure temperature.
You can use a thermometer to find out how warm the air is.
The scale on the thermometer may be in degrees Fahrenheit or Celsius or both.
You can use a rain gauge to measure the amount of rain that falls.
Wind is moving air.
A wind vane, or weather vane, shows wind direction- where the wind is coming from.
An anemometer measures wind speed- how fast the wind is blowing.
Air pressure is the weight of the atmosphere pressing in all directions at a certain place.
Air pressure can change because air particles can move farther apart or closer together.
Weather scientists use a barometer to measure air pressure.
Changes in air pressure mean that the weather is about to change.
Low air pressure usually means rainy or stormy weather.
High air pressure usually means fair weather.
Data are pieces of information, including words and numbers.
After you collect data, you must record them, or write them down.
Data are often recorded in a table or chart.
To prevent errors, it is important to measure and record data carefully.
It is also important not to change the data later.

Weather Maps:

A weather map shows the weather over a part of Earth’s surface.
Weather maps help meteorologists forecast the weather.
A prediction is a guess about what will happen in the future.
Weather maps show temperature and precipitation, and other types of weather data.
When you look at a weather map, you will see a list of symbols called a key.
An air mass is a large body of air with the same temperature and humidity throughout.
There are four basic types of air masses- cold and dry, cold and humid, warm and dry, and warm and humid.
Humidity is the amount of water vapor in the air.
Humid air contains a lot of water vapor.
A front is a place where two different air masses meet.
Triangles show a cold front.
Half circles show a warm front.
At a cold front, a cold air mass bumps up against a warm air mass.
Strong storms happen at cold fronts.
Thunderstorms are likely in warm weather.
In winter, snowstorms are likely.
When a cold front passes over an area, the temperature drops.
At a warm front, a warm air mass meets a colder air mass and slowly rides up over it.
Sheets of gray clouds form at warm fronts.
They often bring rain.
After a warm front passes over an area, the temperature rises.
A stationary front forms when two air masses meet and stop moving.
Clouds and precipitation form at a stationary front.
Weather maps also show air pressure.
The H stands for high.
The L stands for low.
A high is an area of high air pressure.
High-pressure areas usually bring fair weather.
A low is an area of low air pressure.
Low-pressure areas usually bring storms.

Predicting the Weather:

A pattern is something that happens in a regular way you can predict.
Weather is the condition of the atmosphere at a certain time and place.
Weather changes from day to day.
It also changes from season to season.
Climate is the average weather of an area over a long period of time.
An observation is information gathered with your senses.
A hurricane is a large storm that brings very strong winds and heavy rain.