how cold weather kills

[GPSGuided]

and heres a windchill guide with measurements we understand
http://j.ukc2.com/i/208889.jpg

Is humidity an independent variable here?

[wayno]

to a certain extent it will be, high humidity conducts heat faster than low himidity air. i've no idea what the difference is but it is noticeable especially for people who have experienced both conditions... humid cold feels a fair bit colder.

[GPSGuided]

to a certain extent it will be, high humidity conducts heat faster than low himidity air. i've no idea what the difference is but it is noticeable especially for people who have experienced both conditions... humid cold feels a fair bit colder.

Interesting question. Just consulted the Internet. I note that based on the Australian model and assuming my understanding of the equation is correct, higher humidity equates to higher apparent temperature (wind chill temp). The comment was, if the body is wet, then heat will be lost faster. But if the surrounding air is humid, then it'd reduce evaporative heat loss ie. Warmer.
http://en.wikipedia.org/wiki/Wind_chill

[wayno]

in the cold, heat is lost faster because the moisture in the air is capable of conducting heat out of your skin faster.
some people say that theres little noticeable difference once you're going below minus ten if you're wrapped up. but above that it can feel colder especially if the wind is getting in under your clothes...

[GPSGuided]

But the focus here is on wind chill, and how humidity influences that relationship. And based on the equation and explanation given, it should have the opposite effect to what you described ie. Warmer with higher humidity. Guess the other point is, when the temp is low, it's hard for the humidity to come up anyway.

[wayno]

doesnt matter about what the windspeed is, higher humidity will increase the feeling of cold at cold temps...,, even if there is a heating affect it will still be cooling overall

[GPSGuided]

Whilst it's consistent with our experiences, but it doesn't correlate with the mathematical model. Will have to do more reading on this. Curious.

[wayno]

yeah well fine if the mathematicians want to strip off on mt kosiusko at this time of year and test their equations till their little hearts are content....

[GPSGuided]

Just trying to understand whether there's any restraints placed on those equations. It's the researcher in me that got curious. Saving it for the reading time this evening.

[nq111]

to a certain extent it will be, high humidity conducts heat faster than low himidity air. i've no idea what the difference is but it is noticeable especially for people who have experienced both conditions... humid cold feels a fair bit colder.

Interesting question. Just consulted the Internet. I note that based on the Australian model and assuming my understanding of the equation is correct, higher humidity equates to higher apparent temperature (wind chill temp). The comment was, if the body is wet, then heat will be lost faster. But if the surrounding air is humid, then it'd reduce evaporative heat loss ie. Warmer.
http://en.wikipedia.org/wiki/Wind_chill

The steadman chart of apparent temperature on the BOM only goes as low as 20 degrees actual temperature. I concur with the others that at cold temperatures, increased humidity makes it feel colder.

[nq111]

Also, as i understand it, these charts are not based on an true model of human heat loss, but rather a quantitative-qualitative set of observations by people exposed to various temp / humidity combinations and then a best fit line. So one) they will not necessarily be accurate outside the range of temps tested and two) unless a very large sample was used differences in individual's perceptions could be significant variables.

[peregrinator]

This BOM data for current weather on Mount Buller shows how apparent temperature is not necessarily related to wind speed.
(As an aside, I don't recall seeing a 0 km/h wind speed reading at such an altitude very often.)

Temp -1.4 Apparent Temp -3.6 Rel Humidity 99 Wind Speed 0 Wind Gust 0

[wayno]

wonderful little account of the winter of 1812 in russia...

warning: contains graphic content....

http://blog.metservice.com/2013/06/napoleons-winter/

[GPSGuided]

Could not understand why anyone would want to conquer a frozen land when oil and other natural resources weren't prime objectives. Napoleon and Hitler are both irrational.

[wayno]

russia has oil in the caucasus

[GPSGuided]

russia has oil in the caucasus

Yes.

[kanangra]

All right as someone on the wrong side of 50 I will ask the question that no-one else has addressed; at 61 and 54 do you think age was a factor in their inability to survive the night?

K

[wayno]

to a certain extent yes.
as you get older your metabolism slows down, your body doesnt generate as much energy and heat at rest.. metabolism from person to person at that age can vary a lot depending on health.
the people in the article experienced conditions where even a young healthy adult may have struggled to survive, if they were wet through then the odds were greatly against them.
body fat can play a part too, a fit person with less body fat can struggle to stay as warm. in recent years three men had their boat sink on them off shore in new zealand, one was a teenager, the others were middle aged men, the teen died of hypothermia.... the middle aged men had a lot more body fat....

[GPSGuided]

With middle or late-middle age, there'll be some positives and some negatives, all too variable. Aging organs as well as progressive chronic disease states will certainly limit the reserve to survival too. All depends on the individual.

Here's a good summary from Mayo and you still have a good few more years before 65.
http://www.mayoclinic.com/health/hypoth ... sk-factors

[kanangra]

I can certainly vouch for the fact that middle aged men have a lot more body fat.

K.

[wayno]

a healthy young adult can detect temperature changes of half a degree.
in an elderly person this eventually drops to a five degree difference, so they arent noticing gradual drops in temperature. less likely to put on more clothes if they are just using their perception of temperature as a gauge of when to put on clothes

[GPSGuided]

I can certainly vouch for the fact that middle aged men have a lot more body fat.

Question is, are they brown fat or yellow fat?

[wayno]

depends whether your favourite pastime is drinking or walking...

[bailz66]

One of the early stages of Hypothermia is confusion.

So sometimes its too late because you might not realise its cooling down if you leave it too long.

[kanangra]

In my case it is white fat I'm afraid.

K

[nq111]

One of the early stages of Hypothermia is confusion.

So sometimes its too late because you might not realise its cooling down if you leave it too long.

+1

Everyone should have a 'mechanical' plan for what to do if faced with cold conditions approaching dangerous.

Better to stop and get up a tent to get warm a few times unnecessarily than one time keep going, get cold and do stupid things. You may not have the executive capacity left to make the decision to stop and get warm if you wait too long.

[wayno]

i've had hypothermia, digging a snow cave all day in shorts..... by the end of the day i had no energy and no desire to do anything, i was feeling totally lazy (more than usual) couldnt be bothered doing anything like making dinner,
i'd had lessons on hypothermia, and i figured thats what i had, i could easily have just lay down where i was and gone to sleep and that may have been the end of me, i focused on getting my sleeping bag out and getting into it, i still had the presense of mind to know it was pretty important i get into my sleeping bag while i still could. . someone else cooked up dinner for me.... no one seemed to think it was that serious ,, but who knew really, i went to sleep and was lucky that i was able to recover warmth in the sleeping bag and woke up the next morning feeling recovered, but someone should have paid more attention to me to make sure i was ok,, with bad enough hypothermia i may have deteriorated instead... i may have needed someone else in the sleeping bag to warm me up...