Quote:
Originally Posted by kennybobby
Ryan et al,
You guys do know that the pressure reported from the weather channel, etc, is not the real pressure right? They report the altimeter reading pressure at the nearest airport, which is the barometric pressure that has been reduced to sea-level elevation. The pressure in HI would definitely be at sea-level, but Huntsville is about 700' above and the real barometric pressure is less. In Denver it is even lower...Temperature drops about 3 degrees per 1000' elevation, pressure drops about 1 inch Hg per 1000'.
Maybe another topic, but something else to consider is how the reduced pressure affects your mixture ratio, and also the impact of the relative humidity in the air on mixture.
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:::SMACKING MY HEAD:::
You are exactly right. I can't believe I overlooked this... Thank you for bringing it up. Kudos to Kenny!!
To convert it BACK to observed pressure to calculate observed rho, use the following simplified equation (assuming constant temperature lapse rate and gravity):
Po = P*(1-0.0000225577*h)^5.257576
h is the altitude of the observation - and like Kenny said, assume the airport. You can gather the airport observation directly from Google's search page.
I'm going to edit the previous post to include this step.
-Ryan