Ozone from the stratosphere - 10 miles above ground, plunged to the surface producing air quality alerts across southern Colorado on Monday. This is rare. And, it came on top of the intense and destructive winds. Both came from a potent cold front, known as a Bora Front. Cold air is why we had bad air quality on Monday.
It's unusual...but not unheard of, for southern Colorado to get strong cold fronts in May. Typically they occur in winter when weather systems are stronger. The weather term for yesterday's ozone issue is a stratospheric ozone intrusion. Several of you wrote us to ask what this meant - so let's break it down.
The stratosphere is high up in the atmosphere. It varies depending on where you are on the planet and the time of year. At the equator, it's around 60,000 feet up. At the poles, it's around 20,000 feet. In May in Colorado, it's typically around 30,000-40,000 feet. Regardless - the stratosphere is by definition above where most weather systems form and move. Air warms up in the stratosphere. That's bad for storm formation. So it typically acts as a cap on our weather, and the air up there is separated from the air that can easily mix with air you're breathing right now at the ground.
Ozone is a gas. It's three oxygen atoms bonded together. It's great in the sky, bad at the ground. The ozone layer is a zone of high ozone concentration in the low part of the stratosphere. They block out harmful ultraviolet light - the type that burns your skin and causes cancer. So it's a good thing we have it up there!
On Monday, a strong jet stream spread over Colorado as a very cold and dry front moved through the state. The jet stream is also high in the sky, and it's close enough to the bottom of the stratosphere to cause issues sometimes. The strong jet was positioned in a way that it produced mixing of air from the lower stratosphere, and upper part of the lower atmosphere (we call it the troposphere). That was step one. This happens fairly often.
Step two was the upper level low, and very cold dry air. Cold and dry air are both dense - they sink like a rock plopped into the water. This sinking motion captured the ozone that the jet stream had tugged down, and punched it all the way to the surface.
Ozone from any source at the ground is harmful. It can damage your airways, and it's particularly dangerous for those with asthma and other related conditions. That's why we had an air quality alert.
Air mixes down from the stratosphere regularly. It rarely reaches the ground, but it does happen. In Colorado, events like this tend to happen every few years. It's also still being studied. NASA modeleda stratospheric ozone intrusion that impacted Colorado in 2012. So - there ya go. That's how air 10 miles above the ground, caused air quality problems yesterday in southern Colorado.
____
Have a question or story idea you would like the First Alert 5 Weather team to consider? Email: weather@koaa.com
Watch KOAA News5 on your time, anytime with our free streaming app available for your Roku, FireTV, AppleTV and Android TV. Just search KOAA News5, download and start watching.
