Rik O'Shea wrote:
Hello,
my understanding is that air pressure [mb] or [hPa] (metric units
please) descreases with altitude. A rough rule of thumb that I've seen
cited is that the correction is 1 millibar for each 8 meters of
altitude gain.

Looking at the weather for Mixico city in the links below I see an
Air-Pressure 1011.2 hPa or Millibar.

I would have though that the measured air-pressure in Mexico city
(2300 m) would
be of the order of ~ 800 hPa. Can someone enlighten me on this issue ?

Thanks & regards

http://www.wetter.com/home/cooperati...18 2&type=WMO

http://www.bbc.co.uk/weather/5day.shtml?world=0300



Pressures are commonly reduced to sea level. Else a pressure
analysis would just be a topographic analysis. So the pressure
you are seeing at Mexico City is the pressure that would occur
if the alimeter were taken from Mexico City's altitude down
to sea level through a hypothetical atmosphere with an assumed
temperature.

scott