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Curious Kids: What Causes Windy Weather?
Author: Andrew B. Watkins, Manager of Climate Prediction Services. This article was originally published on The
Conversation. his is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions
they’d like an expert to answer. All questions are welcome—serious, weird or wacky!
See the end of the article for how to ask a question.
What causes windy weather? - Jake, aged 8, Melbourne.
Thank you for your great question, Jake.
Wind is just moving air, and air is a collection of different gases. It’s mostly one type of gas, called nitrogen, but also lots
of others, including oxygen – which we need to live.
When air is under pressure, it starts to move – and that causes wind. I’ll explain what I mean by ‘under pressure’.
Imagine you are blowing up a balloon. As you blow more air into the balloon, the pressure builds inside. If the pressure
gets too great, the balloon could pop because the air has nowhere to move.
Just like the balloon, we don’t like to be under pressure, either. Think of when your brother or sister or slightly annoying
cousin gives you a great big bear hug. You feel pressure because you’re getting squeezed. Sometimes that can be nice
but when the squeezing gets too much, the best way to get comfortable again is to break free and run. It’s the same
with air: when it’s under pressure, it tries to escape.
When the air inside a balloon is under pressure and you take your fingers off the neck part of it, the air rushes out—often
with a bit of an embarrassing farty noise. Well, that air rushing out is wind. (And, let’s be honest, it’s why another name
for a fart is ‘breaking wind’).
In the atmosphere, the same thing happens. When pressure builds up in one place, the air rushes to another place
where there is less pressure.
April 2018
But what is causing this pressure in the atmosphere?
Well, as the sun heats up the surface of the earth, some areas get warmer and others stay cooler.
On the whole globe, for instance, the north and south poles are really cold. This is because
sunbeams pass over the top, so not much sunlight actually hits the ground. Compare
this to the equator, where temperatures are really warm, because the sunbeams are
hitting it from directly above.
As you may know, warm air rises - just like when you see hot steam coming out the
top of your kettle or a cooking pot at home.
My old teacher used to say ‘You don’t get something for nothing, Andrew!’ What
he meant was that if air goes up in one place, it must come down in another place.
That other place will be where the air is not rising, and that’s normally where the
cool areas are.
As this happens and the air comes down, it hits the ground and starts to build up. When
that air piles up too much, that pile of air will collapse and spread out, just like air rushing
out of a balloon.
That air will rush towards the area that doesn’t have a big mound of air built up, and that
will usually be a warm place where the air is rising.
You can feel this happening at the beach in summer, where the sun heats up the sand
more than the water. As heat builds up the air rises over the land and starts to fall
over the ocean. Soon there is more air over the ocean than the land, and a breeze
starts as that air pile collapses.
So, put simply, wind is just air moving from one place where there is high pressure to
another place where there is low pressure (a smaller pile of air).
Often, that’s from where it is cooler to where it is hotter. And, thankfully, it rarely makes
that farty sound.
Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult
to send your question to The Conversation. They can email your question to curiouskids@
theconversation.edu.au. Please include your name, age, and which city you live in. You can
send an audio recording of your question too, if you want. Send as many questions as you
like! They won’t be able to answer every question but will do their best.
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