Talk:Atmospheric pressure

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Shwith Density of air (or contrawise)? Duk 07:25, 28 Oct 2004 (UTC)

Contents

[edit] Records

A useful addition to this entry is the normal ranges of atmospheric pressures. From a little research it appears the the maximum recorded atmospheric pressure was in Siberia at 1200 GMT on 31 December 1968: 32.01 in (1083.8 mb). See http://www.weatherwise.org/qr/qry.99.pressure.html

The lowest recorded pressure appears to be in the 920mb area. See http://www.weatherwise.org/qr/qry.lowpressurefollowup.html

Done (I used a more recent reference). Duk 02:57, 20 Dec 2004 (UTC)

this stinks what abbout dgf bearometric pressure??? ?? ?72.68.97.98 14:13, 31 January 2007 (UTC)

(William M. Connolley 10:17, 20 Dec 2004 (UTC)) Can I query this a bit? Presumably, these are SLP's. Well the pacific one clearly is. But the Mongolian one can't be, Mongolia being quite high up. So it must be station pressure reduced to sea level (unless its really an actual reading♥ - unlikely) and reduction to sea level is fraught with difficulties, ie the temperature profile that gets assumed under the ground.
The book didn't specifically say sea level equivalent, but it notes the same Siberian measurement (which is sea level equivalent per the on-line reference) as the second highest pressure recorded. Duk 17:55, 20 Dec 2004 (UTC)
Note I have reduced the precision values of the millibar values. Pressure measurement to 0.01 millibar precision, particularly at the centre of a typhoon, is unrealistic. The value given for Typhoon Tip was obviously a conversion of 25.69inHg, with too many decimal places quoted. I have rounded to the nearest millibar. 143.252.80.110 19:22, 19 October 2005 (UTC)

[edit] To be serious!

Should the article being deleted?
See http://www.mdcc-fun.de/rhythm.university/air.pressure.html.

Yes! Yes! Let's delete it with all haste. Jimp 16Dec05
You're Great! I love you. But, not delete all. Just the air pressure article. Or mention me as the hero who let it come true Steve

[edit] Medical effects

The article is missing info on atmospheric pressure effects on humans (and animals may be). Lower pressure, higher pressure - how does it feels? For older people, sick people, etc.? Paranoid 14:09, 13 Mar 2005 (UTC)


Which effects would you like to have being added to it, to the article? Getting older, in general?

Steve Miller


some effects: pilots in military jets feel sometimes toothache as pressure changes rapidly.


I'm sure this must have other causes. An air pressure, as 'invented' by Otto of Guericke, as a
clue for his hemispheres attempt might not be existing in this nature on the planet.

Steve


Dramatic changes in atmospheric pressure before collision of cold & hot fronts which cause hurricanes or dramatic storms can cause blood pressure in people who are suseptible to it too rise or fall causing unconsiuses,fainting feelings of waitlessness and rolling in a circle the vision in front of there eyes as 50% to 605 of are body mass is water it is not surprising at all.--80.43.21.85 01:01, 3 August 2005 (UTC)


I'm sorry but have you been informed about air pressures origin and today's scientifical advances.

There are lots and lots of hints that, specifically, an air pressure does not match up with todays and by the way, yet, yesterdays observations.

Steve

Hmm, perhaps people could take this issue seriously. Or alternatively, seriously debunk it. Lots of Eastern Europeans who I meet whinge that the air pressure has changed and they have headaches... I reckon they're hypochondriacs so something in this article would be appreciated - even if to say that nothing has ever been proven regarding this whole thing or that it's an old wives' tale. Malick78 (talk) 16:43, 20 January 2008 (UTC)

[edit] Other planets

An extension of the article considering the atmospheric pressure on other planets, notably mars, would be interesting, as a low atmosperic pressure diminuishes the temperature range where water can exist in liquid form.

From phase diagrams found randomly on the internet (and evaluated by moving the thumb) it looks like the average body temperature of a terrestrial bird would be sufficient to boil liquid water given the pressure of the martian amosphere. 84.160.201.148 11:00, 9 October 2005 (UTC)

Sure, the water in the martian atmosphere starts boiling well below the body temperature. But that doesn't mean that the blood in a human body boils instantly when someone is exposed to the martian atmosphere. For a while the pressure inside the body is a lot higher than outside. If you ever be exposed to martian atmosphere you suffocate long before your blood boiled away :-). You won't explode either. But your lung might be ruptured if you hold your breath before you are exposed.

A similar effect, but less of course, is if you ever climb the Mount Everest. The pressure on the top is just one third of the amount on sea level. At this low pressure your cup of coffee will never be more than 70 degrees celsius, because it boils away above that temperature. So, you never burn yourself because you coffee was too hot :-). --Lucius1976 17:56, 12 February 2006 (UTC)

  • i dont think the introduction sentence is very good

Atmospheric pressure is the pressure above any area in the Earth's atmosphere caused by the weight of air. Standard atmospheric pressure (atm) is discussed in the next section.

considering other planetary masses have atmospheric pressures as well... such has Venus and mars. this makes it sound like if I say oh the atmospheric pressure is .6 KPA then... its on earth, when i could be referring to mars. Barcode 16:12, 21 September 2006 (UTC)

[edit] Good Job, Guys

I like the prominently placed formula which gives pressure as a function of altitude. This kind of thing is what makes the difference between a vague discussion and a genuinely useful article. Harkenbane 23:34, 12 October 2005 (UTC)

  • Ok, but rather than an approximation (as is given - and is unclearly cited at that) which only applies for a narrow range of conditions, it would be much more instructive and illustrative if an equation were provided that were general. The equation given is honestly quite confusing in its foundation. The numbers in it are just stated to give it some sense of authority but for all we know they could have been pulled out of a hat. The source cited for this equation is not one that is available to any of us and so cannot be verified. The Wiki standard is then to delete it if it cannot be verified. Please provide a new source, a new equation, or both. Astrobayes 22:09, 18 March 2006 (UTC)

[edit] This article needs updating

This article refers to and links to Standard temperature and pressure ... but it definitely is not consistent with the detailed tabulation in the Standard temperature and pressure article of the various differently defined standard temperatures and pressures in use today. There simply is no longer any universally accepted standard temperature and pressure. We must always clearly state what reference temperature and pressure we are using ... we cannot simply state that we are using standard temperature and pressure, and this article really needs to stress that fact. - mbeychok 06:47, 22 February 2006 (UTC)

It's pretty terrible at the moment. It say standard pressure is 100,000 Pa = 1 bar = 750 Torr, and then goes on to say that "This can also be stated as: [..] 1013.25 millibars" which is obviously wrong; being the value for 1 Atm and not 1 bar. --BluePlatypus 04:59, 7 April 2006 (UTC)


[edit] Standard Atmosphere Redirect

This article should not redirect from Standard Atmosphere. The US Standard Atmosphere is a model (or series of models) of the entire atmosphere including temperature, pressure, density etc (including a definition of sea-level atmospheric pressure). IMHO, fixing this situation would seem to require having Standard Atmosphere be a disambiguation page, pointing to here and the Standard Atmosphere (model). Furthermore, it would be awesome to have a general "atmospheric modeling" page that would contain general discussion and links to NRLMSISE-00, "Standard Atmosphere (model)", and any other related pages (I could not locate any). Comments? MFago 15:18, 7 April 2006 (UTC)

I've begun this work. Any help to flush out US Standard Atmosphere would be appreciated.MFago 13:51, 10 May 2006 (UTC)

You have (of course) noted that there is already an International Standard Atmosphere - which would seem to be the preferable home for an article :-) Linuxlad 19:25, 10 May 2006 (UTC) (The NRL... link may be useful but is unlikely to be easily stumbled on!)

Actually, these models are different (one is from the US, the other is international). I've tried to gather different models on the Atmospheric models page. Thanks for the interwiki link on US Standard Atmosphere though ... the pages I created today are still quite rough stubs MFago 04:11, 11 May 2006 (UTC)

[edit] Frustrated -this page needs useful information.

Unfortunately, this page was not at all helpful to me. You atmospheric scientists likely know all this as obvious, but to those of us who aren't, please help us out. This info. should be easy to find here.

Specifically:

  • A formula for converting height to air pressure (absolute), i.e. pressure=10^(5-height/15500); pressure is in Pascals, height is in meters above sea level.
  • A formula for converting air pressure (gauge) to height, i.e.
  • A formula for converting height to air pressure (gauge), i.e.
  • A formula for converting air pressure (absolute) to height, i.e.

(I didn't write the formulae, and don't want to spend a few days working them out. They should be here to save everyone this work, right?)

  • Graphs of barometric pressure historic data. In addition to the daily variation, what is the seasonal variation? This should be related to height too.

If I had my own barometer, I would have this data. Surely SOMEONE has one and could put this data on the Web.


What are the latest developments in [measuring atmospheric pressure]? Butthole head.

[edit] Removed section

I removed the following section from the end of the article:

Earth's atmosphere is pressing against each square inch of you with a force of 1 kilogram per square centimeter (14.7 pounds per square inch). The force on 1,000 square centimeters (a little larger than a square foot) is about a ton!
But the air inside your body balances out the pressure outside so you stay nice and firm and not squishy.

It was added in this edit and appeared to be out of place (being located after the "See also" section and a template). Since I could not readily find a better location to relocate the text, I will leave it up to those familiar with this article to take appropriate action. Also, for the record, after a quick search, I found very similar text on this NASA site and several other web sites.--GregRM 21:49, 22 June 2006 (UTC)

[edit] Definition of one standard atmosphere: IUPAC and “Purely arbitrary”

  • It is not true to state that “In 1985, IUPAC recommended that standard atmospheric pressure should be 100 000 Pascal…” In 1985, IUPAC did not redefine the value of "one standard atmosphere;" they defined "the standard pressure" at which material properties should be measured.

    * It is not true to state that “this "standard pressure" {one standard atmosphere} is a purely arbitrary representative value for pressure at sea level.” The definition for a standard atmosphere is far from arbitrary and, as a practical matter, truly reflects the mean sea level barometric pressure for many of the industrialized nations (those with latitudes similar to Paris, France).

    * One mm-Hg is not interchangeable with one torr {“(1 atm) is defined as 101.325 kilopascals (kPa) or 760 mmHg”}. A torr is fixed by definition as being precisely equal to 1/760th of a standard atmosphere. The value of a millimeter of mercury is determined by: 1) the definition of gravity (9.80665 m/s2), 2) to the density of mercury (13.595 078(5) g/ml @ 0 °C, NIST value), and 3) to the temperature at which mercury's density is taken. Whereas the value of gravity is fixed by definition, the density of mercury is determined by experiment and is subject to revision. And of course, the temperature of the mercury should be noted in any definition.

    * The attempt to mix-in the specification of gage pressure: {“14.696 psia or 0 psig (pounds-force per square inch, absolute or gauge) (lbf/in²)”} produced two specs that were so intertwined, the line was next-to-impossible to decipher. The most notable problem is it is not spelled "gauge"; it's gage pressure. And gage pressures are always zero so it is utterly meaningless to include them (it) in any specification of atmospheric pressure. Since 1) all the other values were absolute pressures, and 2) none of the other values had equivalent gage pressures, why bother for psi and why bother for any of the others.

    I've corrected these in the article. The values for psi and psf that are now expressed to 15 significant digits have all their terms fixed by definition. Greg L 08:50, 23 July 2006 (UTC)
    • Both "gauge pressure" and "gage pressure" are correct. It depends what country you're from. The former is more common in British Commonwealth countries.--Srleffler 00:37, 17 January 2007 (UTC)

[edit] tidal forcing of atmospheric pressure variation

The statement "Atmospheric pressure shows a diurnal (twice-daily) cycle caused by the tides." should have a reference. please use: Chapman, S., 1970. Atmospheric Tides, Gordon and Breach Science Publishers, NY, ISBN 0677618107


[edit] Mean sea level pressure (MSLP or QFF)

In aviation weather reports (METAR), QNH is transmitted around the world in millibars or hectopascals, except in the United States and Canada where it is reported in inches. ...In Canada's public weather reports, sea level pressure is reported in kilopascals CBC weather, while Environment Canada's standard unit of pressure is hectopascal. [reference or sample please]) Question: If Environment Canada uses the hPa, why is the Canadian aviation weather report still in inches of Hg? Peter Horn 18:37, 7 September 2006 (UTC)

[edit] Observable, Conceptual changes in Air Pressure

Hi, I came here just looking for some basic information on air pressure. Specifically, does air pressure increase when it's about to rain or when it's raining as opposed to during a clear day? Just thought it'd be useful information. I'd add it if I was sure about it. : / --Anon.

[edit] Quran Quotes

Is this really necessary for an article dealing with Atmospheric Pressure? --Eraticus 00:14, 4 November 2006 (UTC)

No, it isn't. And besides, the quote actually refers (indirectly) to air density, rather than pressure. Raymond Arritt 01:35, 4 November 2006 (UTC)

what is the difference between air density and air pressure? air pressure is a result of air density

Please sign your messages with ~~~~. Air density is the (local) mass per unit volume (kg/m3). Air pressure is the force per unit area exerted by the weight of the total column (just about) and is thus N/m2. They are, of course, related, but they aren't the same William M. Connolley 10:24, 7 November 2006 (UTC)

[edit] Pressure vs. altitude

I don't recommend that anyone use the equations given for pressure vs. altitude without checking them very carefully. The user who posted them seems to have converted the units of the universal gas constant incorrectly; there may be other conversion errors etc. Strangely, even the US standard which is cited for this material uses SI units for the universal gas constant. I don't understand why the editor felt it useful to convert them. I haven't reviewed the whole standard, though, so perhaps there was a good reason for it. Ideally, the whole section should be scrapped and replaced with a cited calculation in SI units.

Note that converting a complicated calculation like this from one set of units to another may violate the policy against original research, for precisely the reason seen here: it's easy to introduce errors. --Srleffler 01:27, 17 January 2007 (UTC)

What are you guys talking about? There are no errors and it is not original research. The equations are correct. They are the equations specified by the U.S. Standard Atmosphere of 1976 which was cited. The basic formulae remain the same; only the units changed. It is not original research. It is a simple conversion from metric to standard. The conversion factors are very old and are well-published (refer to NASA SP-7012, The International System of Units: Physical Constants and Conversion Factors). I edited the chart to reflect both SI units and English units. It should now be useful for people who utilize SI units as well as people (like myself) who still use English units. The conversion of the gas constant for air is correct. The conversion is simply "SI units / 0.3048^2" OR "8.31432 x 10^3 N m /(kmol K) divided by 0.3048^2" (note that 0.3048^2 is the conversion factor of square meters to square feet). The only weird thing about all of this is that the U.S. Standard Atmosphere of 1976 uses the value 8.31432x10^3 as the gas constant for air which it admits is not consistent with the cited values of the Avogadro number and Boltzmann's constant. Still though, it uses this value for all it's calculations. The effect of this disparity is negligible (less than 0.08 pascals at 35,000 feet and less than 0.00004 pascals at 250,000 feet) and, in any event, it really does not matter because the actual pressure/temperature at any given altitude is rarely the same as the value in the tables. (Just as the actual pressure and temperature at sea level are rarely 1013.25 mb and 15 degrees celsius on any given day). Still though, it is a realistic, usable average. Additionally, all aircraft flight instruments (worldwide) are calibrated using the same Standard Atmosphere as the reference. Therefore, all altimeters are equally "inaccurate". I feel English units should remain in this article because they are still widely used today. Instrument shops in the United States use inches of murcury and feet when calibrating altimeters; not pascals, millibars or meters. The current, active military standard (MIL-STD-859, Standard Calibration Table For Aeronautical Pressure Measuring Equipment) is tabulated in feet and inches of mercury. Also, the equipment used to calibrate the altimeters are themselves calibrated using feet and inches of mercury (refer to Air Force technical order 33D7-3-60-71). In Europe, however, they use SI units. The chart in the article now shows both so everyone should be happy. It should also be mentioned that the U.S. Standard Atmosphere of 1976 is identical to the ICAO standard up to 32 km and the ISO standard up to 50 km. Sincerely, Matt Gould 132.19.75.25 19:06, 27 January 2007 (UTC)

I think there's no problem using English units as well, but aren't the English using degrees Fahrenheit in stead of Kelvins, ounces in stead of grams and pounds in stead of kilograms? (Well, the latter two are nitpicking, since they only occur in constants, but then, L is (partially!) converted as well.) Another point is this: does the model rather than just a mean value also give an error (e.g. standard deviation)? The example calculation looks suspiciously accurate to me. Sluys (talk) 16:29, 23 February 2008 (UTC)

[edit] Variation in thickness of the Earth's atmosphere

Mountaineers are interested to know more about the variation in barometric pressure due to the varying thickness of the Earth's atmosphere. I think this thickness variation is due to centrifugal force effects of the Earth's rotation.

Specifically, mountaineers would like to know:

What is the variation in sea level barometric pressure between the pressure at the equator and:
a)10 deg latitude
b)20 deg latitude
c)30 deg latitude
d)40 deg latitude
e)50 deg latitude
f)60 deg latitude
g)70 deg latitude
h)80 deg latitude
i)90 deg latitude

DO ANY OF THE BAROMETRIC PRESSURE EQUATIONS TAKE LATITUDE INTO ACCOUNT? Would the variation be about the same for the northern versus southern latitudes?


These pressure differences are related to items of interest to mountaineers such as:

Is the air less dense at the summit of Denali (20,320') than on Aconcagua (22,841') due to the higher latitude?

Chimborazo(20,000'+)is on the Equator in Ecuador. Thus it sits on the "bulge" caused by the Earth's rotation and is said to be the summit farthest from the center of the earth. Which effect is greater on the density of the atmosphere on Chimborazo: the "height" due to the bulge, or the greater thickness of the atmosphere at the Equator? In other words, would the air on Chimborazo be less dense if it were located at higher latitude?

On a high summit, say 20,000', would the air be more dense on a cold day or a warm day? (It would seem that if it were warm, the atmosphere would expand and more air would be above you so the pressure would be greater. Conversely it would seem that on a cold day, the air would be dense and would contract, thus more of the total atmosphere would be below your 20,000' location and so the pressure would be less at your 20,000' location.)


Can someone add more info on this topic to the main article? Ice axe 2 20:36, 31 August 2007 (UTC)

[edit] Image Removed

I removed the image at the top of the page because it didn't illustrate the article and was confusing. The items on the graph were not identified, and it was unclear what was even being represented. Basically, the article is more clear without the image than with it. The image remains in the commons area. Victor Engel (talk) 22:02, 14 December 2007 (UTC)

Yes, but... the image is still referenced in the text of section "Local atmospheric pressure variation." And it was kind of a nice example, though I agree it needs to be better explained/described. And it (or an improved replacement) should be placed within the section where it is discussed.Wahoctb (talk) 03:50, 13 February 2008 (UTC)

[edit] More generalized case

I've been trying to work out a formula similar to those in the article, relating change in pressure to change in altitude, for cases in which the change in the acceleration of gravity varies significantly enough to be taken into account. For a first step, I'd assume the mass of the atmosphere between the two altitudes to be insignificant, i.e. the source of gravity could be considered a point source. Since, assuming I do work it out, it apparently couldn't be included as original research, if anyone can find a well-sourced formula for this and include it, that might be appreciated by some, certainly myself.

I think expressed as a function, it might look something like P(m,r,M,T), with the variables being pressure, mass of central object, distance from central object (both radius for gravity, and used as altitude), molar mass of gas, and temperature. Constants involved would be G and R, the gravitational and gas constants. Bonus points if you can account for a temperature lapse rate, too. -- J. Randall Owens | (talk) 08:05, 15 December 2007 (UTC)

[edit] Records

I removed the records paragraph:

"The highest recorded atmospheric pressure, 108.6 kPa (1,086 mbar or 32.06 inches of mercury), occurred at Tosontsengel, Khövsgöl Province, Mongolia, 19 December 2001.2[not in citation given]
The lowest recorded non-tornadic atmospheric pressure, 87.0 kPa (870 mbar or 25.69 inches of mercury), occurred in the Western Pacific during Typhoon Tip on 12 October 1979.2[not in citation given] The record for the Atlantic ocean was 88.2 kPa (882 mbar or 26.04 inches of mercury) during Hurricane Wilma on 19 October 2005."

because the citations are not valid. Superm401 - Talk 04:47, 12 January 2008 (UTC)

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[edit] Calculating Variation With Altitude

Not all land areas are at or above sea level. Some are significantly below sea level, like the Dead Sea region. I think it might be useful for this section to make some mention of whether the variation in air pressure below sea level is consistent with the variation above, i.e. would you add the same amount of air pressure at 400 meters below sea level as you would subtract at 400 meters above? Berberry (talk) 16:36, 5 April 2008 (UTC)