/ Can you answer this question?

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themountaintamer - on 06 Oct 2012
So this is my question that I am seriously confused/ stuck on. I think I have the answer but not sure.


If the temperature at 194m above sea level is 8 C and you were at 995m on a very wet and windy day, with a wind speed of 10km per hour, what wind chill temperature would you expect? (Please show your calculations)

Expecting that it is wet therefore be cloudy my calculations would be as follows:
995 194 = 801
801 / 200 = 4.005
Knowing that on a cloudy day air temp. cools at -1 for every 200 metres.
-1 x 4.005 = - 4.005
8 - -4.005 = 3.995 C
Temperature at 995m = 3.995 C

What do you think, some clarification please.
Al Evans on 06 Oct 2012
In reply to themountaintamer: I think you are being much too simplistic, thare are no hard and fast values for the variations. When we were on Everest West Face in 1988 the lead team were pushing out the route in temps which the wind chill calculations gave as -90C. They were functioning as normally as could be expected in ordinary down clothing, I have to seriously doubt it was -90C, though maybe they were just supermen, they were SAS after all :-)
aultguish on 06 Oct 2012
In reply to themountaintamer: just doing a rough guesstimate, I also arrive at 4c(ish) but do you not now have to factor in the airspeed to get the windchill temp?
themountaintamer - on 06 Oct 2012
In reply to aultguish: Thats also what I thought but cant find or figure out how to do that. Been staring at my books and the internet to find out but struggling. Cheers
Flinticus - on 06 Oct 2012
In reply to aultguish:
Yes, certainly wind speed will be one of the main factors in calculating wind chill.
Gog the Mild on 06 Oct 2012
In reply to themountaintamer:

The table in Wikipedia http://en.wikipedia.org/wiki/Wind_chill is in F, but by eye it suggests that a wind of 10kph at 4C will have a wind chill effect of about -2C. So the wind chill temperature would be approximately 4C - 2C = 2C. Quite balmy for walking.
martinph78 on 06 Oct 2012
In reply to themountaintamer:

windchill = 1.2 degrees celcius
martinph78 on 06 Oct 2012
In reply to Al Evans: I read that windchill doesn't continue to get colder past -40 celcius (I think I remember that as the correct figure).

So once windspeeds continue to increase past that point it has little effect on the actual windchill. Wish I could find where I read it, hopefully someone will be along who has teh reference to hand!
AdrianC - on 06 Oct 2012
In reply to themountaintamer: Your original calculation allows for the lapse rate (6 deg C per 1000m is more common rate for wet air) but not windchill. The calculations for windchill are so varied and are for such limited conditions that they're hard to get useful results from. For example the American one doesn't take humidity into account whereas (oddly enough given the general climate) the Australian one does. I've never really run into anyone trying to use this stuff practically for clothing decisions or even route planning beyond getting a general idea of how unpleasant it will be in an exposed spot. Lapse rate calculations, on the other hand, can be a good way to work out where's going to be good climbing / skiing / avalanching etc.

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