Summary of ideas:
All weather on earth originates with the Sun.
The Sun warms some areas of the Earth and the air more than others. Warmer air rises and cooler air sinks.
Pressure differences arise as the air masses move, and compress or thin out. Air moves from high to low pressure areas.
Moving air is wind.
As air moves, water in the air can condense or freeze, giving rise to precipitation.
Some air movement patterns give rise to weather phenomena, such as tornadoes and lightning storms.
We can forecast the weather by measuring air temperature and pressure, as well as humidity (amount of water in the air).
The systems are complicated, so predicting weather is not always accurate.
Suggested activity order:
Set up frost cans.
Seasons model to show why we have seasons: the Earth is tipped at an angle and so the Northern and Southern hemispheres get more or less light depending on the Earth's position around the Sun.
Summarize: Sunlight hitting the Earth and heating the land and water is how weather starts. Different amounts of sunlight on different parts of the Earth leads to different kinds of weather.
Return to frost - see the dew formed on the top of the can, and the frost formed on the botton of the can. Both the dew and frost came from the water in the air, either condensing (dew) or freezing (frost).
Summarize: Air has water in it, which condenses to a liquid or freezes to a solid when the air cools.
Four fast (5 minute) stations for student groups to move through, looking at why air moves, what happens when it moves, and how we can measure it.
1. Measuring temperature
Students use thermometers to measure water and air temperature.
After the stations, summarize: different air temperatures make air move.
2. Air pressure in a bottle.
A surprising activity that works by air pressure differences.
After the stations, summarize: air moves from high pressure to low pressure, creating winds and moving rain from place to place.
3. Turbulence activity in sealed bottles.
This activity uses water to model what happens when air masses move. If fast moving air meets slow moving air, or if air moves over a mountain range, the air will start to make swirls and eddies - called turbulence.
After the stations, summarize: Airflow can make complex patterns, sometimes hard to predict.
4. Tornados.
Sometimes moving air stays in a pattern for a little while, making a weather phenomenon.
After the stations, summarize: Air patterns make weather.
Review the station results, and summarize as above.
Bottom line: temperature differences give rise to pressure differences, which moves air, which along with the water in the air, makes weather.
End in a circle for mini lightning.
Alternative activities to fold in:
Show how the Sun heats the Earth unevenly:
Heating land and water activity shows how land heats up faster than water.
Sun's angle on earth demonstration shows how the Sun's light and heat hitting Earth depend on the position on Earth.
Summary: the equator is heated more than more northern or southern latitudes (because of the angle of the sun's rays), and the land is heated up more than the water (because the land heats up more quickly).
Question to students - what colour reflects light more - light or dark? Snow and ice reflect the light and the heat, whereas the darker forests absorb the light and heat, so are heated up more. The sun is also unevenly heating up the darker and lighter areas of earth.
The land heats up the air above it, and the result of the uneven heating of earth is that some areas will have warmer air and some areas cooler air. These warm and cool air masses move.
Show movement of warm and cold fluids: warm/cold/salty water flow activity models how air masses interact when some are warmer than others. It will also model how the water in the oceans moves around, when some parts of it are warmer or colder or more salty.
In the atmosphere, this movement of warm air upwards and cooler air downwards generates winds.
In the oceans the movement of colder and saltier water downwards and warmer water upwards generates ocean currents that moves heat with them and affect the climates on land.
A simpler demonstration showing how warm water (and air) rise is the convection demonstration.
Image of the global air circulation patterns showing the air rising at the equator and falling further north and south where it has cooled (e.g. https://en.wikipedia.org/wiki/Hadley_cell#/media/File:Earth_Global_Circ…)
Live interactive map of Earth’s winds across the surface: https://earth.nullschool.net/#current/wind/surface/level/orthographic=-…
