Displaying items by tag: solar radiation
Why is it so cold? Simply put, cold is caused by the absence of heat. Sometimes conditions are such that there is much less heat in an area. For instance:
Snow cover reflects solar radiation. That means, that if the ground is covered in snow, even on a sunny day, the sun doesn't warm the earth because the sunlight is reflected back into space.
Shorter amount of daylight mean less time for the sun's warming rays. Plus, during the winter season, the sun strikes the earth at a sharp angle, meaning the sun's rays are spread out further (less concentrated), so they have less warming power.
Lack of cloud cover at night allows heat to escape into space. While I love those beautiful winter nights when the sky is clear and the stars are bright, I know that the lack of cloud cover means that any heat that may have accumulated during the day will be lost to space. When there are clouds, the cloudcover helps to trap the heat in the troposphere (lower level of the atmosphere).
The jet stream brings cold air down from the Arctic. The jet stream is a meandering band of air that circles the planet. (There are four jet streams circling the planet from west to east - two polar jet streams and two tropical jet streams) Click here to see a short animation (from NASA) of the jet stream. Sometimes, the polar jet stream dips further south, due in part to increased snow cover across large areas of land - which means... less heat.
“Bitter cold” is a term that’s getting a lot of use this winter – and with good reason. The word bitter – while typically used to describe something that has a disagreeable taste – means something that causes a harsh or stinging sensation, which is exactly what very cold weather will do.
With a high of -15º forecast for Monday (January 6th), and wind making it feel even colder, I think it’s safe to say that Monday’s cold will be bitter indeed.
From a health standpoint, there are many reasons to be cautious when venturing outside in this weather:
Hypothermia. This is defined as the body temperature dropping from the normal 98.6º below 95º. Hypothermia can occur when outdoors in extremely cold weather for a long period of time, even if dressed warmly. It can also occur rather quickly when someone is outside for even s short period of time if they are not dressed for the cold. Symptoms of hypothermia include shivering, slurred speech, irrational behavior, shortness of breath and eventually, unconsciousness.
Frostbite. Freezing temperatures can cause exposed part of the body to lose feeling and color. Nose, ears, cheeks, chin, fingers and toes are the most likely to be affected. In extreme cases, frostbite will lead to amputation. Symptoms to look for include numbness, skin that feels unusually firm or waxy, and skin that appears white or grayish-yellow.
Heart attack. If you have a heart condition, high blood pressure, or a family history of heart disease, be careful not to over-exert yourself if shoveling snow. Sudden physical exertion in cold weather – which occurs when lifting and throwing a heavy shovel full of snow – has been linked to heart attacks. Take lots of breaks to rest and warm up.
- Falling down. I’ve fallen down once this winter due to slipping on icy pavement. I wasn’t hurt, but I know several people who have broken wrists, hips, arms and ankles due to slipping on ice. A couple of tips to avoid slipping on ice:
1) wear shoes with good traction. If you don’t have any, invest in slip on traction devices like Yak Trax – they work like chains on tires by providing metal cleats that bite into the ice to keep you from slipping.
2) Use a walking stick, preferably one with a pointed tip. This will improve balance while walking across a slick surface.
If you do find yourself falling, try to remember not to put your arms out to catch yourself – that is the cause of most wrist and arm fractures when falling. Instead, try to remember to tuck your arms in, relax your body and roll so that you land on your shoulder and then roll onto your back. The rolling motion helps dissipate the energy from striking the ground. Trust me, I’ve done this, and it does work.
In general, there are commonsense steps you should take to stay safe in the bitter cold:
Wear a hat. Mom was right – wearing a hat in cold weather is one of the smartest things to do, as a lot of heat will escape through your head if you don’t.
Dress in layers – layers trap air between the layers, and air is a great insulator.
Stay dry. If you get wet, change into dry clothes as soon as practical. Moisture will speed heat loss.
Eat food and drink water. Being outside in the extreme cold causes the body to burn more calories. Also, the air holds less moisture as the temperature drops, so it is important to make sure your body is well hydrated. But, avoid alcohol – it can cause your body to lose heat more quickly.
If driving in the cold, be sure to have your cell phone with you, as well as a set of jumper cables, a bag of sand or kitty litter for traction if needed, and an ice scraper.
Finally, when it is cold, don’t leave your pets outside for very long, unless there is a sheltered, warm spot that they can go into. Pets can get hypothermia and frostbite just like people!
photo by Gail Moreland, taken at TLC's Weers Conservation Easement as part of the Art of the Land Photo Contest in 2012.