Wind-chill Activities
Background:
When working in Antarctica the already cold conditions can be made to feel even colder due to effects of wind-chill. When the air temperature is less than that of the body heat transfer will occur with the body loosing heat to the surroundings. There are 3 ways the body can loose heat to its surroundings.
- Radiation (this is worse if you have sunburn!)
- Conduction (e.g. by lying on the snow)
- Convection (moving air carrying heat away from the body)
Convection is the primary way heat is lost from the body in Antarctic conditions, so it is important to minimise the amount of moving air coming into contact with the body by layering clothes to trap insulating, stable air.
The faster air moves over the body, the more heat it can take away. This is what is meant by wind-chill. The table below shows that small changes in wind speed have a big effect on wind-chill.
| Windspeed | Equivalent Temperature (oC) | |||||||||
| km/hr | mph | knots | m/s | |||||||
| 94 | 58 | 50 | 26 | -76 | -62 | -47 | -33 | -26 | -19 | -12 |
| 76 | 47 | 40 | 21 | -72 | -58 | -44 | -30 | -23 | -16 | -10 |
| 54 | 34 | 30 | 15 | -66 | -53 | -39 | -26 | -20 | -13 | -7 |
| 36 | 22 | 20 | 10 | -59 | -47 | -34 | -22 | -16 | -10 | -4 |
| 18 | 11 | 10 | 5 | -51 | -39 | -28 | -17 | -11 | -6 | 0 |
| 11 | 7 | 6 | 3 | -47 | -36 | -25 | -14 | -9 | -4 | 2 |
| Air Temperature (oC) | -40 | -30 | -20 | -10 | -5 | 0 | 5 | |||
Activities:
Wind Chill
It is hard to measure the effects of wind chill but it can be done by wetting pieces of material and wrapping them around a small frame that allows a thermometer to be put in the middle. Use a fan/hairdryer to blow air through the material and use a thermometer to measure the temperature just in front of the material box in the wind and then inside the box in the wind. The moisture in the material should allow a difference in temperature to be detected. Test different materials to see how effective they would be against wind-chill if they were wet.
Wind Proofing
To investigate how effective different sorts of materials and combinations of materials are at blocking the wind a simple experiment can be set up using a small electric fan or hairdryer set on cold. Set up the fan on a bench in line with a small piece of paper held vertically by a bulldog clip at the bottom. Behind the piece of paper place a board with angles marked on it to measure how far the paper is blown over by the fan. Record the deviation from the vertical by the fan alone then place sections of different materials in between the fan and the paper, record how far the paper bends over for different materials and combinations of different materials to see who can find the most windproof combination. The less the paper leans the more wind proof your clothing.
Suggested materials: thermals, polar-fleece, wool, down jacket, windproof clothing, and cotton.
Acknowledgements:
ANARE First Aid Manual 6th Edition, Australian Antarctic Division (2002)
