Practical Backpacking™ Forums

Welcome to Practical Backpacking™ Forums (PBF).

You are currently viewing PBF as a guest which has limited access. By becoming a PBF member, you will have full access to view and participate in tens of thousands of informative discussions, to view links and attachments (photos), and will gain access to other special features. Registration is fast, simple and absolutely free! Click to Become a PBF Member! Be sure to also explore the Practical Backpacking Podcast.


Go Back   Practical Backpacking™ Forums > Practical Backpacking™ Trailhead > The Trailhead - General Backpacking Discussion
HOME FAQ PBF GUIDELINES BLOG PODCAST GALLERY STORE CALENDAR Mark Forums Read

The Trailhead - General Backpacking Discussion The Trailhead General Discussion forum is for backpackers to discuss non-gear related wilderness backpacking issues (e.g. technique, LNT, hiking partner wanted, trip planning...) that are not covered in other PB forums.


Reply
 
Thread Tools Display Modes
  #1  
Old 03-10-2008, 08:01 PM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
0nelove 0nelove is offline
Practical Backpacking™ Junior Member
 
Join Date: Nov 2007
Posts: 63
Is 20 degress at altitude "colder" than 20 at sea level?

Is it harder to stay warm at altitude because the air is less dense, meaning fewer air molecules to retain heat, than if one was at sea level? So while the temp gauge may say 20 in both circumstances, if you're at 10K feet it will be much harder to stay warm, right?

Just wondering if that is correct or not?
Reply With Quote
Please Consider PBF Sponsors
  #2  
Old 03-10-2008, 09:02 PM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
WildlifeNate WildlifeNate is offline
Practical Backpacking­™ Forums Moderator
Backpack: Osprey Atmos 50
Sleeping Gear: DIY down quilt
Shelter: ENO Doublenest Hammock, WB Bugnet, GG Tarp
 
Join Date: Mar 2006
Location: Nacogdoches, TX
Posts: 1,610
I can't say that my experience correlates with your thoughts. Granted, I've not spent much time at that altitude in cold temperatures. Mostly fairly warm summer temps for me. Still, I have spent a little time at altitude in subfreezing temps and I haven't found it any more difficult to stay warm. 20 degrees is 20 degrees.

PV=nRT (pressure*volume= (amount of gas)*(gas constant)*temp)

In that context, for the temperature to be the same in the same volume, (understanding that the gas constant does not change), the pressure and amount of gas will be different.
Reply With Quote
  #3  
Old 03-10-2008, 09:05 PM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
yippikiyo yippikiyo is offline
Practical Backpacking­™ Forums Moderator
 
Join Date: Sep 2006
Location: Texas
Posts: 485
I can share personal experience that humidity
Makes cold air feel colder. You may find more humidity at sea level
yippikiyo
Reply With Quote
Please Consider PBF Sponsors
  #4  
Old 03-10-2008, 09:22 PM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
big_load big_load is offline
Practical Backpacking­™ Forums Moderator
 
Join Date: Apr 2006
Posts: 1,825
I've been qualitatively trying to balance the differences I would expect in conductive, convective, and radiative heat transfer. I would expect conductive heat loss to decrease at altitude, convective to be the same (or slightly less) for the same wind velocity (although velocities might average higher at altitude) and radiative I expect to vary too much with local terrain.

However, what is probably much more of a factor is metabolism. While heat loss might not be much different, your body's efficiency in generating replacement heat can degrade at altitude, so in that sense staying warm can be more difficult.

I'm sure there are good data to be found on both aspects that would quantify the differences, but I don't have any at hand.
Reply With Quote
  #5  
Old 03-11-2008, 09:01 AM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
Random_Walker Random_Walker is offline
Practical Backpacking™ Regular Member
Backpack: Arc'Teryx Needle 65
Sleeping Gear: WM Ponderosa
Shelter: MH SkyLedge
 
Join Date: Apr 2007
Location: The PNW
Posts: 182
Quote:
Originally Posted by big_load
However, what is probably much more of a factor is metabolism. While heat loss might not be much different, your body's efficiency in generating replacement heat can degrade at altitude, so in that sense staying warm can be more difficult.

Yup, Spending time at altitude, above the alpines stunted trees in the world of rock I do tend to eat more to stay warm. I can also lose quite a bit of weight if I do not watch it when I am at altitude.
Reply With Quote
  #6  
Old 03-11-2008, 09:47 AM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
0nelove 0nelove is offline
Practical Backpacking™ Junior Member
 
Join Date: Nov 2007
Posts: 63
I found on another website that there is a decrease in thermal insulation the higher you go. I think at 10,000 feet it was estimated to be %9. BMR was also said to increase.
Reply With Quote
Please Consider PBF Sponsors
Aquaponics 4 You
  #7  
Old 03-11-2008, 01:34 PM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
sirtimbly sirtimbly is offline
Practical Backpacking™ Junior Member
Backpack: REI UL 45
 
Join Date: Jan 2008
Location: Colorado Springs, CO
Posts: 29
I'm mostly guessing here, but I think the biggest difference in warmth you will feel at altitude is due to what's going on inside you body, significantly less oxygen in your bloodstream can really affect your warmth. Your metabolism will slow down some, but I think the biggest problem is less O2 carrying blood flowing to the tissue in your extremities. So yes, I think I am naturally colder sleeping at altitudes of 9-11k feet because of the thinner air even though I am acclimated to living at 6,000 feet. Also, I sometimes get sick at high alititudes, so that will really mess up your night too.
Reply With Quote
  #8  
Old 03-11-2008, 05:48 PM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
WildlifeNate WildlifeNate is offline
Practical Backpacking­™ Forums Moderator
Backpack: Osprey Atmos 50
Sleeping Gear: DIY down quilt
Shelter: ENO Doublenest Hammock, WB Bugnet, GG Tarp
 
Join Date: Mar 2006
Location: Nacogdoches, TX
Posts: 1,610
Quote:
Originally Posted by sirtimbly
I'm mostly guessing here, but I think the biggest difference in warmth you will feel at altitude is due to what's going on inside you body, significantly less oxygen in your bloodstream can really affect your warmth. Your metabolism will slow down some, but I think the biggest problem is less O2 carrying blood flowing to the tissue in your extremities. So yes, I think I am naturally colder sleeping at altitudes of 9-11k feet because of the thinner air even though I am acclimated to living at 6,000 feet. Also, I sometimes get sick at high alititudes, so that will really mess up your night too.


You may have less oxygen in your bloodstream (at extreme altitude, maybe, but I'm not sure about 10-11k), but your body is going to be compensating for the lack of oxygen in the air by increasing respiration and heart rates. This would correspond to 0nelove's comment about BMR increasing. This is why, and when BMR increases, you actually increase your heat output.

Quote:
I found on another website that there is a decrease in thermal insulation the higher you go. I think at 10,000 feet it was estimated to be %9. BMR was also said to increase.

I am not quite sure what is meant by a decrease in thermal insulation? Are you saying that the R value of a given insulation (sleeping pad, for example, where such values are measured) is lower at higher altitude? Or are you saying that it requires less insulation to achieve a certain degree of warmth all else being equal?

It seems to me that it would depend on the type of insulation being used. Considering a sleeping pad where the air inside is sealed from the outside, it seems to me that it wouldn't necessarily work this way. Also it seems like denser fill insulations (say, something with lots of hollow fibers) would be less affected than looser fill insulations (like a high loft down) because they tend to trap air more effectively (albeit at a higher weight).
Reply With Quote
  #9  
Old 03-12-2008, 09:45 PM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
0nelove 0nelove is offline
Practical Backpacking™ Junior Member
 
Join Date: Nov 2007
Posts: 63
The article said that more insulation is required because the air is less dense, meaning there are less molecules of air to act as part of the insulation (remembering that all insulation really does is keep warm air from moving away from the body). Same reason that the difference in temperature at altitude can be significantly different between sunlight and shadow I suppose.

So simply put, R values decrease.
Reply With Quote
  #10  
Old 03-18-2008, 01:37 PM
© 2006-2016 Practical Backpacking™ / All Rights Reserved
Radnord Radnord is offline
Practical Backpacking™ Regular Member
 
Join Date: Aug 2007
Location: Washington
Posts: 81
There are so many variables at play that I doubt if there is one definitive answer. At 10,000' on Mt. Rainier, the contrast between being in the sun, and having a cloud pass between you and the sun is sharp and instant. I have not experienced that near sea level. I don't know if that is because the sun feels hotter since there is less density and atmosphere to filter the sun's rays, or if because the lack of sun is causing a faster heat transfer due to altitude.

This was on a calm day. If the wind is blowing, it seems to me that the wind chill factor would be the same regardless of altitude.

Essentially 20 degrees is 20 degrees and many other factors such as level of exertion, metabolism, moisture content of clothes, and such will determine how you feel.
Reply With Quote
Reply


Thread Tools
Display Modes

Forum Jump



All times are GMT -7. The time now is 04:27 PM.

Backpacking Forums


Powered by vBulletin Version 3.5.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © 2006-2017 Practical Backpacking™
Practical Backpacking is a trademark of Absolutely Prepared™
Practical Backpacker is a trademark of Absolutely Prepared™
Practical Backpacking Podcast is a trademark of Absolutely Prepared™
Practical Backpacking Magazine is a trademark of Absolutely Prepared™