wind-chill factor (WCF)
wind-chill factor (WCF)
(OP)
I was used to the definition of WCF as the cooling effect of a combination of temperature and wind velocity, expressed as the heat lost by the skin surface exposed to higher convection heat transfer coefficients, depending on the body size, shape and metabolic rate. Re-reading an old thread I saw a possible relation of WCF with the cooling effect by sweat evaporation, which I belief applies to the body's reaction to warm weather. Would the experts clarify this point ?





RE: wind-chill factor (WCF)
see:
http://www.answers.com/topic/wind-chill
and
Definitions of Wind Chill Factor on the Web:
The apparent temperature which describes the cooling effect on exposed skin by the combination of temperature and wind, expressed as the loss of body heat. Increased wind speed will accelerate the loss of body heat. A wind chill factor of 30 degrees or lower on exposed skin will result in frostbite in a short period of time.
www.weca.org/nws-terms.html
The amount of cooling one "feels" due to the combination of wind and temperature. The formula to calculate wind chill is: WC=.0817(3.71 V^.5 + 5.81 - .25 v)(T-91.4)+91.4 where V=wind speed in MPH and T=temperature F.
ggweather.com/glossary.htm
A calculation that takes into account the effect of the wind to provide a reading of the apparent temperature (as opposed to the actual temperature as registered on a thermometer).
www.hometravelagency.com/dictionary/ltrw.html
Effect of wind blowing away the warmed air near the body.
www.carlwozniak.com/clouds/glossary.html
a factor applied to temperature that attempts to better represent the feel of low temperature, wind and humidity on people
w
Wind chill is the apparent temperature felt on the exposed human (or animal) body due to the combination of air temperature and wind speed. ...
en.wikipedia.org/wiki/Wind_chill_factor
good luck!
-pmover
RE: wind-chill factor (WCF)
I think that statement is just plain wrong- the actual temperature needs to be below freezing. If it's 50 degrees, you may die from hypothermia, but you won't get any frostbite, no matter what the wind is.
RE: wind-chill factor (WCF)
although it seems unlikely or difficult to believe, be assured that it is possible for individuals to suffer from frostbite at 30°F or lower - exposed flesh. just ask any snow machiner whom has ridden in those temps. it may take awhile, depending upon heat removal rate from skin and other individual human biological factors, but it has and can occur.
-pmover
RE: wind-chill factor (WCF)
RE: wind-chill factor (WCF)
thanks for the clarification! apology's to JStephen.
-pmover
RE: wind-chill factor (WCF)
Really important if someone robs you of your clothes while skiing, though. Otherwise, just a weather persons term.
rmw
RE: wind-chill factor (WCF)
I guess we would be more comfortable with it in terms of BTU/(ft^2*R*sec).
David
RE: wind-chill factor (WCF)
I don't know why the weather people can't just say, "It feels like 40F and 20 miles/hour out there." Why do they have to combine it into a single Wind Chill number that nobody understands and is deceptive?
I saw in a newspaper the other day a weather report that had the "Real Feel" temperature index. It purported to included temperature, wind speed, humidity, altitude, barometric pressure, and the metabolism of the reader. I wondered how they knew my metabolism before I bought the paper. Perhaps it should also include the gender of the reader. My wife always thinks the room temperature is too hot and I always think it is too cold, and we are sitting in the same room. Shouldn't that be included in how cold a temperature "feels"?
RE: wind-chill factor (WCF)
The concept is no less or more valid at high temps than at low. But you will NEVER hear a weatherman say "It is 90, but the wind chill is 78"- doesn't sound impressive, so no point.
RE: wind-chill factor (WCF)
David
RE: wind-chill factor (WCF)
Keep the wind the same, the ambient temperature the same, and vary only the relative humidity, and the WCF changes.
That is why the WCF is much more pronounced on the bone dry high altitude ski slopes (where you better not have too much skin exposed for too long) and the same temperature on the Texas Gulf coast.
Same with heat index which the weather people fall in love with in the summer time. Opposite effect here. On humid days, moisture does not readily evaporate from the skin, making it feel hotter than it really is. Same temperature in Utah, and it feels a lot different than the Texas Gulf Coast.
rmw
RE: wind-chill factor (WCF)
http://en.wikipedia.org/wiki/Wind_chill
According to this, current "wind chill temperature" is reported based on wind velocity and temperature only. Humidity, density of air, and radiation heat transfer have nothing to do with the reported number, although they obviously do affect the actual and perceived coldness.
As pointed out in this link, the wind chill factor was originally worked out for human faces (not human bodies). The wind chill factor varies depending on the surface it's applied to- so faces, wet rubber, and monkey heads all have different wind chill factors. The orientation of a surface in the wind would affect wind chill, so your face will have a different wind chill factor on the upwind side than on the downwind side (wonder which they based it on?) If you have a beard, the wind chill factor would be different. If you're fatter or skinnier, have higher or lower metabolism, etc, the factor would vary. It varies with height above the ground. Not surprisingly, different people disagree about how it should be defined- because it's not just a simple rate.
The equation listed in the link is:
Twc = 35.74 + 0.6215Ta - 35.75V^1.5 + 0.3275TaV^0.16
where Twc = wind chill temperature, Ta = actual temperature, both in F, V = wind speed in mph.
RE: wind-chill factor (WCF)
And, I'll add one.
A 40 degree F wind, whether blowing hard enough to make human exposed skin think it is 28 or minus 28 will only cool a dry object to 40 degrees F, (or whatever approach temperature is relavent). If the object is wetted, then the wet bulb temperature will be reached (approached). And that is dependent upon the relative humidity.
rmw
RE: wind-chill factor (WCF)
RE: wind-chill factor (WCF)
http://www
RE: wind-chill factor (WCF)
rmw