Talk:Humidity
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[edit] does this graph help ??
http://en.wikipedia.org/wiki/Image:Abs_humidity.gif#file
please note that it may be erroneous, it is based upon formulae by Sonntag/Wexler, although my application could be incorrect, however I have checked it and to me it appears correct, any confirmation would be gratefully received though :) Teeteetee 21:00, 8 August 2006 (UTC)
[edit] humidity and density
A few changes here - liquid water is heavier than air yes, but is it more dense? as a liquid yes, but not so simple any more. Alos, cleaned up some of the writing, we don't need to take the author on a story about the cubic metre of gas, after all, if we have a fixed volume of a cubic metre, and flow in and out of it, you can in fact have more molecules than you previously had in that volume (maybe for a short time more molecules collide and bump each other into that box, than in the previous timeframe). Anyway, doesn't matter, as the point is, water vapour is lighter than N2 and O2, the whole cubic metre thing and the flow doesn't really help the explanation imho. --Phatmattbaker 13:43, 24 July 2006 (UTC)
{FAOL tags) -- deleted - Hard Raspy Sci 01:57, 15 December 2005 (UTC)
The above can be deleted, I read German, and nothing in the english wiki source is left out here from other wiki topics (english version). Ie. some stuff in the German article may be considered off topic in the English version...as other articles cover the same stuff...see water vapor. The only thing I can see is that this article needs editing, if it is to remain combined from 3 articles. ---- Hard Raspy Sci 05:04, 15 November 2005 (UTC)
[edit] Request for more information :-/
How is the ideal humidity
Yes, what is the ideal humidity, for comfort/health, indoors? That is why I came to this page (humidity), but I can't find an answer
Agreed. A bit abstract, guys. I came here so I could understand the weather forecasts.
Thermal_comfort has the info, but it's in jargonese. According to Weatherman Steve [1] people feels best at a dew point temperature between 50 - 60° (which he translates as 31-41% relative humidity if the air is 90° ) Gaviidae 23:14, 21 November 2006 (UTC)
[edit] Keep it simple
- Absolute humidity is the quantity of water vapor in the air expressed by weight.
- Specific humidity is the quantity of water vapor in the air expressed by a ratio of water vapor to dry air.
- (Such a ratio might be 1:200, for example). That would specify that the air contain one part water vapor and 200 parts dry air.
- Relative humidity is the quantity of water vapor in air expressed by the use of a percentage.
- This method is the cause of a great amount of confusion of the subject of humidity. Now that computers have been created which can access a database and display absolute humidity figures and specific humidity ratios in the blink of an eye, the relative humidity method may soon be replaced by one of the other methods, which do not introduce any confusive quality.
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- Each percentage point is applicable to the qualities of the air which are present at a specific moment. Any change in air temperature or air pressure instantaneously changes the capacity of the air to hold water vapor. Every combination of air temperature/air pressure has its own maximum amount of water vapor that the air will hold.
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- At the same air pressure, the maximum amount of water vapor in air (expressed as 100%) is much greater at high temperatures.
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- At the same air pressure, very cold air at -40 degrees C (-40 degrees F) has the capacity to hold very little water vapor. Nevertheless, the maximum amount of water vapor will be expressed as 100% relative humidity.
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- The same amount of water vapor that is expressed as 100% relative humidity at -40 degrees will be expressed as only 20% or 10% or 5% or 1% (et cetera) at certain other warmer air temperatures.
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- Supersaturation, where the capacity of air to hold excessive quantities of water vapor is present, is an unnatural condition which may be ignored since it does not ever occur in the Earth's atmosphere, normally. Keep it simple.
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- 141.151.140.116 11:51, 16 August 2005 (UTC)
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I agree with "keep it simple" and to the point, however Relative Humidity will never go away, especially due to its highly important property that defines condensation. Absolute and Specific do not do that, but that does not degrade their importance either.
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- Hard Raspy Sci 04:45, 15 November 2005 (UTC)
- Ok, did a lot of edits...don't pay attention to the summaries on the history page, they may not make sense. Still needs more work though...
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- Hard Raspy Sci 06:13, 15 November 2005 (UTC)
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[edit] NSDL
NSDL is temporarily down do not edit unless permanent. Thanks - Hard Raspy Sci 01:55, 15 December 2005 (UTC)
[edit] The opposite of sweating
Is it possible to extract heat from humid air by extracting the H2O ? [Is it possible to extract heat from humid air, then use this heat to warm the air, draining the water (now a liquid) that was once just a vapor (ie liquidise the vapor)] Teeteetee 12:05, 16 March 2006 (UTC)
- Of course :) Air conditioners do this :P Gaviidae 23:05, 21 November 2006 (UTC)
- Yeah, ... :) ...but do Air conditioners use the heat(energy) extracted from the air to warm the air being conditioned ?(ie not cooling the inside air, but warming it)Teeteetee 05:52, 8 February 2007 (UTC)
[edit] practical question
In that warmer air holds significally more water than cooler air. The practical question seems to be - how much more water is held in the air at increasingly varing temperatures.
Given usual and similar pressure and other conditions, what is the relationship of the relative amount of water that can be held at say 90% humidity at 70F degrees versus 80F, 90F, 100F and 110F.
Is there a general formula? Does air at 90F hold twice as much water as 70F?
Air does not hold water.
The Antoine equation is a emperical formula that can be used to estimate the saturated vapor pressure of water (and other substances for tha matter) at different temperatures and pressures.
Go here: http://antoine.frostburg.edu/chem/senese/101/liquids/faq/antoine-vapor-pressure.shtml.
For the question asked. At 90F the saturated vapor pressure of water is 0.699 psi(a); at 70F it is 0.363 psi(a). 0.699/0.363 = 1.9. So an air/water mixture at 100% RH at 90F has approximatly 1.9-times the that of a mixture at 70F.
(A good rough rule of thumb is that a 10 degree (C or K) increase in temperature roughly doubles the saturated vapour pressure, i.e. the amount of water held as vapour in the air. -DGB)
[edit] Measurement
I added a section on remote sensing of humidity, and an external link to a more detailed discusssion. KonaScout 23:55, 10 October 2006 (UTC)
[edit] Footnote
Can we get that Optiks footnote out of the middle of the page and moved down to the bottom? I can't figure out why it is where it is now, but it looks stupid. 82.93.133.130 09:07, 29 November 2006 (UTC)
- Done. Vsmith 11:53, 29 November 2006 (UTC)
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- Thanks-- now that I see how you did that, I can do it on the next one : ) 82.93.133.130 22:55, 2 December 2006 (UTC)
