Wind chill

Blimey o' Riley its cold, really cold. It's that windchill factor that the weathermen keep talking about. Today was about 0 degrees C but with the wind chill factor it 'felt like' -6 degrees.

Today that wind really is bitter and it is the wind that really makes the difference.

The body is at a temperature of 37 degrees and usually, well always in the UK, the temperature is below that. This means that the human body will lose heat to the environment wherever there is exposed skin. Heat is lost in three ways, conduction, convection and radiation. As the heat is lost it warms up a layer of air above the skin. If this air remains in place it acts as a insulating blanket making it harder for more heat to be lost.


http://xc7.xanga.com/c8f89be5680a0189785432/b13039054.gif

However, when a wind is blowing this warmed up air is being continually removed thus maintaining a large temperature gradient allowing heat to be lost more rapidly. This makes the homeostatic mechanisms of the body respond, causing shivering, vasoconstriction, a desire to wear warm clothes and goose pimples and a feeling of cold.

There is even a equation for working it all out:

Twc = 13.12 + 0.6215Ta - 11.37V(+0.16) + 0.3965TaV(+0.16)

where T_{\rm wc}\,\! is the wind chill index, based on the Celsius temperature scale, T_{\rm a}\,\! is the air temperature in degrees Celsius (°C), and V\,\! is the wind speed at 10 metres (standard anemometer height), in kilometres per hour (km/h).

All I know is its really quite cold.

 

Comments

Post a Comment

Popular posts from this blog

Sparkly bathroom prevented by natural chemical equilibria

Image
I have had the pleasure of cleaning the bathroom today. I have used a number of different products over the years to find a chemical that will remove the annoying marks from the tiles, taps and shower screen. The hard water means that no matter how clean and sparkly I get the taps, they are only two showers away from being once again covered in the annoying white powder.   Crystals of limescale (http://en.wikipedia.org/wiki/File:Kesselstein_k.jpg) There is a lot of interesting chemistry involved in limescale. It is essentially deposits of insoluble calcium carbonate left behind from the hot water. But how does it get into the water in the first place and why doesn't it stay in it? Limescale initially starts as limestone, chalk and other similar sedimentary rocks that formed from the bodies of tiny calcium containing sea creatures that lived in warm shallow tropical seas millions of years ago. See the BBC clip at this learning zone site. Since their formation these rocks have been
Read more

Polka dot, 7 inches, 15 minutes, luke warm

Image
January 2010 and a new craze hit Facebook. Across the social network women started to post colours as their status. Some posted beige, some ivory, some hot pink, some polka dot. For a while people across the world were confused, intrigued, indeed fascinated by what these colours could mean. In fact the colours referred to the colour of the bra the woman was wearing that particular day. This 'craze' was in aid of a breast cancer awareness campaign a fantastic cause and in my opinion a clever and innovative use of Facebook. Over the last couple of days some of the ladies have begun to post a length measured in inches followed by a time in minutes. This has resulted in a status that might read '6 inches 25 minutes'. Oh how amusing...I like a bit of smut but I found these updates strangely annoying. Obviously it doesn't mean what it says and is code for something fairly inane and boring. So slightly intrigued and determined to crack the code I did what I always
Read more

What's Your Station?

Image
One of my most vivid memories is completing my Silver Duke of Edinburgh Expedition in the New Forest one October half term. It must have been 1987 as Mike Smith was the Radio 1 breakfast host and I remember cooking bacon on the Trangia stove, in a field behind a scout hut in Fordingbridge, whilst listening to T'Pau's new single China in Your Hand, it was a gorgeous Autumn morning.  http://asymptotia.com/wp-images/2007/08/Radio_dynamo.jpg I had a red plastic battery operated radio that we listened to as we walked. That radio once got us into trouble on a snowy February in Dartmoor as the magnet in the speaker affected our compass, a rookie error that put us out a couple of miles searching for a postbox on Rough Tor.   Radio 1 was the station to listen to, the new music was heard first on this station, and alongside Mike Smith the line-up included Simon Bates, Mike Read, Simon Mayo and of course Steve Wright. Whilst at Uni I still enjoyed listening to Simon Mayo's breakfast
Read more