Courtesy vgm8383Its really cold where I live these days. It was 23 below zero Celsius (this is a science blog) this morning when I woke up. Bitter cold. An interesting phenomenon happens on roads when it gets this cold, a condition called black ice. It was in full effect this morning, with Twin City roads having over a dozen accidents and causing lengthy commute delays.
So, what is black ice (besides an AC/DC album)?
Black ice is a type of ice that is usually thin and forms without bubbles inside, making it harder to see. Because of its transparency, it usually takes on the color of whatever it is on, making it doubly hard to see and a hazard to drivers, bikers and walkers.
Black ice on roads is most common at night or in the early morning when temperatures are at their lowest, and before the sun has had a chance to warm the road surface. It can be mixed in with a wet road, and it can be hard to tell the difference between a road that is wet and a road that has black ice. Black ice can form more easily on bridges and overpasses as the very cold air can cool both the top and the bottom of the road at the same time, causing it to cool below freezing more quickly. Black ice can form from any source of moisture – light rain, meting and re-freezing snow or any other source of moisture on a road surface.
Here are some tips for driving on black ice. Drive safe my fellow Minnesotans – I’m going to be on the road with you this evening!
Courtesy Aaron SilversThis afternoon, in an announcement that surprised all, a rural Pennsylvanian groundhog emerged from a tree stump cage, and used magic to tell the world that it would be under the icy yolk of winter for at least six more weeks. Residents of the planet’s southern hemisphere were particularly disturbed.
Wisely deviating from the over relied upon scientific discipline of meteorology, experts have turned to the prognostications of the groundhog Phil, who uses centuries old magical techniques to reveal the secrets of immensely complex future weather patterns.
The determination was not without controversy, however. While the groundhog weather diviner West Indies Wilbur agreed with Phil – the most senior and important of extra-sensory rodents – several noted groundhogs took issue with the announcement. Wiarton Willy, Staten Island Chuck, Sir Walter Wally, Shubenacadie Sam, Malverne Mel, General Beauregard Lee, and Balzac Billy all argued the proclamation. However, as the National Climactic Data Center has stated groundhog accuracy to be around 39%, it makes sense that so many weather rodents would disagree with shrewd Phil.
This afternoon I saw a bald eagle circling over Irvine Park, just to the west of the museum. We're lucky: we see eagles a lot here in Minnesota and along the museum's stretch of the Mississippi River. Have you seen any eagles this winter? When and where?
It’s finally getting into real winter conditions here in Minnesota, but that still doesn’t mean it’s winter as normal.
Sunday’s snowfall led to three snowmobile crashes on lakes where drivers went through thin ice or open water. In one case, the snowmobile driver died. According to the press accounts, many snowmobile drivers like to “skip” their machines over open water. It got me wondering how this actually works.
It’s actually much like how a stone that is thrown at the right angle and speed skips across open water. Checking the web for snowmobile sites, I found out the specific details.
The snowmobile skip formula works this way: In order to skip, the snowmobile must be going at least 5 mph for every 150 lbs. of vehicle (or fraction thereof). For example, if a snowmobile and rider weighed 780 lbs., it would have to be going at least 30 mph to skip. The distance of water a snowmobile can cross is 2", plus 1/2" for every 5 mph over the minimum skip-speed. If the above-mentioned snowmobile was going 45 mph, it could cross 3 1/2" of water; at 75 mph, it could cross 6 1/2" of open water. There’s also friction, or drag, involved in this formula. A snowmobile decelerates 5 mph for every inch (or fraction) of water it "skips." The snowmobile above, crossing 6-1/2" inches of water at 75 mph, would be going only 40 mph when it got to the other side.
A snowmobile cannot change direction while "skipping" -- it can only go in a straight line. If a snowmobile doesn't make it across the open water, it sinks. It only takes one second for a snowmobile to sink to the bottom of a lake or river.
So, as they say on all the stunt shows, don’t try this at home….or on a lake near your home. Across the U.S. and Canada each winter about 50 people die from snowmobiles crashing and sinking into frigid waters.
Interestingly, a graduate from the University of Minnesota is developing a way to minimize the deaths of snowmobilers falling through the ice. John Weinel is now working with university students to come up with an automatic floatation device that could deploy from a snowmobile, much like an airbag in a car, when a snowmobile crashes into water. That work has already led to floatation equipment law enforcement officers can use at the scene a snowmobile water crash to help keep victims at the surface until better equipped rescuers can get to the scene.
Of course, the best thing to do if you're driving a snowmobile is to avoid driving it anywhere there is a chance to be open or thin ice. You and your snowmobile will be able to get around better and happier if you never go sinking into chilly water.
It's cold this morning. Maybe the coldest morning of the season so far? Luckily, there's also a lot of sunshine, and almost no wind.
If it were windy, you'd hear the weather forecasters talking a lot not only about the air temperature (-6 degrees when I left the house), but also about the "wind chill." Wind chill is a way to describe how quickly heat is transferred from your body to the atmosphere when it's both cold and windy outside. As wind increases, more heat is drawn from your body, decreasing your skin temperature and eventually your internal body temperature. Wind chill makes it feel much colder than it actually is.
Last year, I overheard a woman in the Science Museum parking garage elevator talking about how she parks her car in a sheltered area to protect it from wind chill. She was worried that, if she left it in a more exposed area, it wouldn't start. I can't say anything about the state of her car battery, or condensation on her distributor, but I can say that wind chill has very little impact on cars or any other inanimate objects: wind will shorten the time it takes for an object to cool to the temperature of the surrounding air, but it won't get any colder than that no matter how much wind there is.
For humans and animals, though, wind chill affects how quickly hypothermia and frostbite can occur. Hypothermia is a condition in which core body temperature has fallen to the point where normal muscle and brain functions are interrupted. (Thor did a post about hypothermia a few weeks ago.) Frostnip/frostbite are conditions in which body tissues freeze. Knowing the wind chill helps us make decisions to avoid these and other cold weather dangers.
The best thing to do when there's a significant wind chill is to stay inside. But you can't stay at home on the sofa all winter. So what can you do? Dress right when you go outside. That means wearing several layers of loose-fitting, lightweight, warm clothing. (Trapped air between the layers will insulate you and keep you warm.) Stay dry. (Remove layers if need be to avoid sweating and later being wet and cold.) Wear a tightly woven, water repellent, hooded top layer. Cover your mouth to protect your lungs from the cold. Mittens, which allow your fingers to share warmth, are better than gloves. And your mom was right: wear a hat! Half your body heat can be lost from your head.
As the recent news accounts of the missing hikers on Mount Hood reminds us, hypothermia and other impacts of extended exposure to snow can have drastic impacts on us.
So what exactly is hypothermia, anyway?
You’re probably well aware that our optimum body temperature is 98.6 degrees F. That’s the best and most efficient temperature for chemical reactions to take place in our body, reactions that keep our body working.
When our body temperature goes below 98.6 degrees, those reactions slow down. The colder our body gets, the more severe the impacts will be on our body. And it doesn’t take too much of a change in our body’s core temperature to have significant impacts on our bodies.
The first stages are considered mild hypothermia – when your body’s core temperature drops to 96 degrees F. Characteristics that show up in that stage are shivering and difficulty in doing complex motor actions (like skiing or skating). You can still walk and talk without difficulty.
The second stage, moderate hypothermia hits when your body’s core temperature ranges from 95 to 93 degrees F. Symptoms that can set in at that stage include dazed consciousness, loss of fine motor coordination (difficulty zipping up a coat, for instance), slurred speech, violent shivering and irrational behavior. In some cases of that last symptom, people will start to take off their clothes, unaware that they are actually cold.
If you don’t start to warm up, you’ll head into severe hypothermia – when body core temperatures can range from 92 - 86 degrees and below. These temperatures are immediately life threatening. You personally probably wouldn’t recognize these symptoms if you had them, but they include shivering in waves, falling to the ground and assuming the fetal position, muscles becoming rigid, skin becoming pale and pupils dialating. At around 90 degrees of core body temperature, the body actually goes into hibernation, shutting down blood circulation to the outer extremities with heart and breathing rates reducing. At 86 F, the body becomes a “metabolic icebox.” The person will look dead, even though their inner body is still active.
The tricky thing with hypothermia is, the farther you go into it, the less you’ll be able to recognize it. But should you come upon someone suffering from severe stages of hypothermia, here’s what you can do.
With some help, using the person’s body is the best way to warm him or her up. First may sure the person is dry. Then create a shell of total insulation for the person. That can include sleeping bags, blankets or wool clothes. Don’t worry about having too many layers. A four-inch bundle of insulation around the person works great. Don’t ever put the hypothermic person in a sleeping bag with another person.
Other things to consider are fuel for the body. In severe hypothermia, the stomach shuts down. But getting warm fluids into the cold body will have a great impact. Give a suffering person a mixture of warm water with sugar every 15 minutes. Those nutrients will be absorbed right into the blood stream and help create more body heat to warm the body. Let the person urniate as well. After the urine has left the body, more internal body heat will be directed to heat up other organs.
What can you do to prevent hypothermia? First off, wear plenty of warm, water-proof clthing when you know you’ll be out in cold weather. Also, use the buddy system with another person to check each other’s face, cheeks and ears for signs of frostbite. Do a regular self-check on yourself for cold areas, wet feet, numbness or anesthesia. If you discover a cold injury, warm up that area as soon as possible.
There is probably no day greeted with greater joy and anticipation than the first day of spring -- especially after a Minnesota winter! Sometimes, the only thing that gets us through February is knowing that better days are on the way. But when, exactly, does spring get here?
TV weathermen will tell you that spring starts on the vernal equinox -- the day when the number of hours of daylight are equal to the number of hours of night. (In 2005, this falls on March 20.) The problem is, the weathermen are wrong.