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Warm, cold and the polar vortex

Believe it or not, December 2013 was one of the warmest ever for the planet

Snow and a barbed wire fence.

The global weather numbers are in for December 2013, and it turns out that despite the cold weather parts of North America have been experiencing, the planet on a whole continues to be running a temperature.

According to data from the U.S. National Oceanic and Atmospheric Administration’s (NOAA) National Climatic Data Center, NASA and University of Alabama-Huntsville’s (UAH), and Remote Sensing Systems, December 2013 was one of the top five warmest on record. NOAA placed December as the third warmest, NASA had it as the fourth-warmest, while UAH had it as the second warmest. This was the ninth consecutive month with a top-10-ranked global temperature, making 2013 the fourth warmest year on record globally since reliable records began in 1880. If you include 2013, then nine out of the 10 warmest years globally have all occurred in the 21st century, with the one other year occurring in 1998.

I know this is little consolation when we are freezing our butts off here in Manitoba. After another ground blizzard created hazardous conditions across a large portion of southern and central Manitoba last weekend, it’s hard not to question global warming. Then, once you get your mind around the global aspect of global warming and look at the maps showing who has been above and below average, your thoughts start going in the direction of, “It’s just not fair.” But that’s the thing about temperatures: if one area is seeing temperatures warmer than average, another area will be seeing cooler than average. This is especially true in the winter. So far this winter, most of the Northern Hemisphere is seeing above-average temperatures, which means all that displaced cold air has to go somewhere — and that just happens to be here!

As I travelled around during the week, I heard a lot of self-proclaimed weather experts discussing why we’re seeing all of this cold weather. I’ve heard ideas ranging from Arctic/Antarctic ice cover, and the hole in the ozone layer, to the infamous polar vortex. The one I’ve heard about most, and that has probably grabbed the most headlines, is the polar vortex. So I thought we should spend a little time examining just what a polar vortex is — and can it be blamed for all of this cold weather? After all, we seem to have this need to blame things on something.

A polar vortex is a large area of circulation (low pressure) in the upper atmosphere that is centred near both poles and tends to be the strongest in the winter. The counterclockwise flow around this region in the Northern Hemisphere means the atmosphere is flowing from west to east. The stronger the air flowing around the vortex is, the more circular the vortex tends to be. If the flow weakens, the shape of the vortex tends to get distorted and we start to see large ridges and troughs form. Ridges are regions where the vortex has pulled northward, allowing warm air to move northward, while troughs are areas where it sags southward, allowing cold arctic air to push south.

The polar vortex has been around for — well, for as long as we’ve had the ability to measure the upper atmosphere. It’s likely it has always been a part of the world’s overall weather patterns, so it is not a new thing. Even the term “polar vortex” has been used in the literature since at least the 1930s.

Stuck in the middle

So, the question now is: Are the cold temperatures a result of the polar vortex? The answer is yes and no. The polar vortex forms as a function of the cold temperatures that develop over our poles in the winter as a result of little to no solar input during this time of the year. The polar vortex, depending on the strength of the winds flowing around it, can create troughs and ridges that can allow cold air to surge southward. The polar vortex is not the only feature that can influence troughs and ridges, so we can’t really say the current setup of troughs and ridges is directly connected to the polar vortex.

The pressure pattern we have been basically stuck with since early December across North America has been dominated by a large and persistent ridge of high pressure over the West Coast and a deep trough of low pressure over eastern North America. Warm air is pushing north under the western ridge and is bringing record temperatures all across the far western parts of North America. To our east, the trough is allowing cold air to sag southward, bringing some of the coldest winter weather in years to eastern regions. That leaves us kind of stuck in the middle. Actually, we are mostly under the eastern trough, with Saskatchewan really in the middle. Either way, this means we will continue to see storm systems ripple down the dividing line between the warm and cold air. If this dividing line pushes to the east, we’ll see warmer air move in and better chances for snow; if it slides to the west, we’ll see colder and drier air. I’m just not sure which of the two situations I like better. Personally, I’d rather see the West Coast ridge move eastward and bring us an early end to this cold, blowy winter!

Daniel Bezte is a contributor for the Manitoba Co-operator

About the author

Co-operator contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.



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