I know I started our annual look at severe summer weather last week, but I had a basic weather question from one of our younger readers that simply asked what wind is and why has this spring been so windy, at least across parts of the Prairies. Such a simple yet fundamental question. So, I am going to take a short break from our severe weather series and take this moment to try and answer this question.
Before we do, April’s global temperatures have been crunched, and it turns out April was the second-warmest on record according to NOAA, NASA and the European Copernicus Climate Change Service. Global land areas saw their warmest April on record while global ocean temperatures were ranked second. So far, the first four months of 2025 comprised the second-warmest start to a year with records going back 176 years.
Currently, there is about a 40 per cent chance that 2025 will be the second only to last year in terms of warmth and a 99 per cent chance that it will end up being in the top five warmest years.
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Whipping up wind
OK, now onto this week’s topic of wind. There is one constant aspect of weather that pretty much everyone on Earth has experienced no matter where they live, and that is wind. So just what the heck is wind and more importantly what causes it to blow?
There are three main categories that we can use to classify winds. The first category is the primary winds that consist of the general circulation of the atmosphere (westerly winds for example). The second category is secondary winds, which are winds associated with the movement of high- and low-pressure systems. The third and final category of wind is the tertiary winds, which include such local winds as the Chinook winds in Alberta.
But really, the question was what is wind and what actually causes the wind to blow? As with most things in our atmosphere there is a simple answer that explains the basics, but when you get right down to it, even the reason for wind blowing can get fairly complex. In this week’s article we will keep things basic and simply go into the four main factors that control the wind.
Before we do that, let’s take a short pause and actually define what we mean by wind. After looking up literally a dozen different definitions of wind, the one that I thought was best was probably the simplest: wind is the horizontal movement of air across the Earth’s surface with turbulence occasionally causing a vertical component to this movement. Sounds reasonable. Now onto the four main driving forces behind the wind.
The first and most important force that helps drive our winds is actually one of the weakest forces in nature — gravity. If we didn’t have any gravity on the Earth, then the atmosphere wouldn’t have any weight. Without weight, the atmosphere would not compress itself and there would be no increasing density as you get closer to the Earth’s surface. This would mean that without gravity there would be no atmospheric pressure. Heck, there wouldn’t even be an atmosphere.
When discussing weather, we often discount gravity or simply remove it and simply say it is a given. Instead, we just call the force of gravity acting on the atmosphere, atmospheric pressure. That would then make atmospheric pressure as our number one top force driving the wind. Actually, it is the difference in atmospheric pressure that creates the wind, or what we call the pressure gradient force.
In reality, this is really what drives our wind. Wind is the result of the atmosphere trying to balance out differences in air pressure.
The best way to think about this, in my opinion, is to picture two large pails held at the same level side-by-side. One pail is full of water while the other is empty. If we were to connect the two pails with a hose at the bottom of each pail, the water from the full pail would flow into the empty pail. Why? Because there is a pressure difference between the two pails. The bigger the pressure difference the faster the water will flow. This same analogy holds true for our atmosphere, the bigger the difference between areas of high (full pail of air) and low pressure (empty pail of air or rather a less full pail of air), the faster the air will move between them. The faster the air flows, the greater the wind speed.
Well, that pretty much describes why we have winds. So why are there two other forces involved? Well, as we dig deeper into what drives winds, we will discover that the Coriolis force complicates things by deflecting winds as they travel across the globe. Remember I pointed out there is a basic and a complex understanding of wind? Now we are getting into the complex area. Due to the Earth’s spin, air that is moving across the surface will get deflected to either the left or the right depending on where you are on the Earth. More on this in the next issue.
Finally, there is that insidious force called friction, the subtle force that slowly drains away energy from any and all systems. Even within the weather there is no getting away from this sinister force.
OK, maybe I’m being a little too melodramatic. After all, without the force of friction, we wouldn’t be able to shelter ourselves from the wind, and the weather as we know it would not be the same. This force slows winds down over bumpy terrain such as forests but has little effect on wind speeds over flat spaces like open prairies and water bodies.
I’ll dig deeper into these two forces in the next issue and how it all ties together to give us wind.
