Do these help? http://nssdc.gsfc.nasa.gov/space/model/atmos/us_standard.html
The ICAO standard atmosphere for the continent of North America, based on summer and winter averages at latitude 40� assumes the following conditions: 1. The air is a perfectly dry gas. 2. A mean sea level pressure of 29.92 inches of mercury. 3. A mean sea level temperature of 15�C. 4. The rate of decrease of temperature with height is 1.98�C per 1000 feet. http://history.nasa.gov/SP-367/chapt2.htm -----Original Message----- From: Pat Naughtin [mailto:[EMAIL PROTECTED] Sent: Wednesday, April 21, 2004 15:45 To: U.S. Metric Association Subject: [USMA:29598] Re: Air pressure history Dear Mike, No, I had no response. As you can see, I have reposted this to the USMA list. Maybe someone there can help this time. Cheers, Pat Naughtin LCAMS Geelong, Australia -- on 2004-04-21 23.11, Michael Payne wrote: > Did you ever get an answer to this Pat? > > Mike Payne > > >> [Original Message] >> From: Pat Naughtin <[EMAIL PROTECTED]> >> To: U.S. Metric Association <[EMAIL PROTECTED]> >> Date: 18/7/03 10:33:26 >> Subject: [USMA:26410] Air pressure history >> >> Dear All, >> >> Does anyone know the history of 'standard' air pressure of 29.92 inches of >> mercury (inHg) or 760 millimeters of mercury (mmHg). >> >> When I looked at the values that have been used previously I found: >> One atmosphere of pressure is equivalent to: >> 760 millimeters of mercury >> 29.92 inches of mercury >> 14.7 pounds per square inch (psi) >> 1013.25 millibar (mb) >> 34 feet of water (approximately 10 meters of water) >> >> Thinking that the 'standard' air pressure might be a mid-point between >> high >> and low pressures, I investigated to find that: >> The lowest air pressure recorded at sea level was 87 kilopascals, and >> the highest air pressure recorded at sea level was 108.4 kilopascal, but >> the mid-point between these values is 97.7 kilopascals, and this doesn't >> seem to fit with any of the previously used 'standard' values. >> >> I then thought that 10 metres of water might be a clue. Taking the >> standard >> value of acceleration due to gravity (g) as 9.806 65 metres per second >> squared, I found that the pressure below 10 metres of water is about >> 98 kilopascals, so I had no luck there either. >> >> Can anyone help with the history of 'standard' air pressure? >> >> Thanks, >> >> Pat Naughtin LCAMS >> Geelong, Australia
