Weather

Objectives

• Describe and illustrate the water cycle and associate parts of the cycle with weather conditions.

• Observe and describe changes to the properties of water when it is heated or cooled and associate these changes with weather conditions

• Observe and describe the interactions between air and water in the atmosphere

• Describe weather in terms of temperature, precipitation, humidity, wind speed and direction

• Create and use tools that measure relative humidity and wind speed and direction

Materials

• see individual activities for materials.

Background

If weather were a recipe, the key ingredients would be solar radiation and water; and the atmosphere would be the large mixing bowl. Heat from the sun causes water to evaporate and rise up into the atmosphere. As it cools in the atmosphere, water condenses back into a liquid (clouds), then precipitates.

WEATHER AND CLIMATE

What’s the difference between “weather” and “climate”?

Weather is the state of the atmosphere at a particular time and place. Daily changes in the weather are driven by differences in temperature, moisture and air pressure.

Climate refers to the prevailing weather trends and typical conditions over a long period of time. People who study weather have a different occupation title than those that study climate:

• Meteorologists study current weather conditions and develop forecasts. Weather forecasting is a prediction of what the weather will be like next hour, day or week.
• Climatologists study data and indicators of historical climates either over centuries or eons. They also make predictions about changing climate patterns in the future.

ALL ABOUT AIR

To understand weather we need to understand the properties of air and our atmosphere. It is changes in air pressure that create the weather we experience.

Even though air is invisible it’s made up of a lot of stuff (gas molecules & particulates) and it has weight. The force of gravity pulling air towards the Earth generates atmospheric pressure. Atmospheric pressure depends on the amount of air above the location where the measurement is taken, and so while atmospheric pressure is 1kg per square centimeter at sea level, it drops as you go higher. Changes in air pressure create wind and affect the evaporation and condensation rates of water—condensation that creates the fog, clouds, rain, snow, hail and sleet that affect our daily lives.

Vocabulary

Air Pressure: The weight of air pressing down on earth.
Atmosphere: A layer of gases surrounding a planet. The Earth’s atmosphere is dividedinto five layers: exosphere, thermosphere, mesosphere, stratosphere, and troposphere.
Barometer: An instrument that measures air pressure.
Barometric Pressure: Air pressure indicated by a barometer.
Clouds: A visible collection of tiny water droplets or ice crystals suspended above the Earth’s surface.
Condensation: The change of water vapour to liquid water. The opposite of evaporation.
Convection: Motions in a fluid that transport and mix the properties of the fluid.
Evaporation: The process of changing a liquid (like water) to a vapour. The opposite of condensation.
Fog: Cloud cover that contacts the ground. A reported weather condition which reduces visibility.
Humidity: The amount of water vapour (gaseous state) in the air.
Hygrometer: An instrument that measures the water vapour content of air or the humidity.
Meteorologist: A scientist who studies and predicts the weather.
Meteorology: The study of the atmosphere that focuses on weather processes and forecasting.
Precipitation: Water in any form falling from clouds. This includes rain, hail and snow.
Relative Humidity: The ratio of water vapour contained in the air compared to the maximum amount of moisture that the air can hold at that specific temperature and pressure.
Smog: Visible air pollution in urban areas.
Unstable Air: Air that is warmer than its surroundings and tends to rise, leading to the formation of clouds and precipitation.

Other Resources

EnvironmentCanada | Skywatchers: Interactive meteorology for Students and Teachers

Environment Canada | Air quality health index

University Corporation for Atmospheric Research | Center for Science Education | Web Weather for Kids | Cloud Types

Scholastic | Teachers | Weather watch

Scholastic | Kids | Interactive weather maker

National Geographic Video| Weather 101

Government of Canada | Climate Change

Kids Code Jeunesse | YouTube | How to Measure Wind & Water with Microbits

Weather Wiz Kids

CanTeach | Weather songs & poems

The Weather Channel