November 11, 1998 transcript # 259-3
Subject(s): brainstorm, barometric pressure
Title: Brainstorm Answer: Barometer

Hi, I’m Dave Thurlow from the Mount Washington Observatory for The Weather Notebook. We had a brainstorm a few weeks back that asked how one might measure the height of the Seattle Space Needle, using a weather instrument. A barometer, an anemometer, a thermometer, … whatever. Well this question proved to me that a lot of you folks were paying attention in high school Physics, and most of the answers suggested the application of the old 'air gets thinner as you go up in proportion with the change in height' trick and hence the use of the barometer.

Steve Moser: "If you use a barometer, you find out atmospheric pressure."

That’s Steve Moser of Flat Rock, NC, who listens to WNCW.

Steve: "And by knowing the pressure at a given height, from the equation Pressure=rohGH…

Now, wait a second-- wait a second. This is one of the basic equations of meteorology. In fact it’s so basic that scientists call it primitive. ( jungle sounds ) No, not that kind of primitive, but primitive as in of prime importance. The equation just says that as you go up the air pressure goes down. It’s a balance and because of this, if you know the pressure you can solve the equation and get the height… remember that’s what were looking for. OK take it away Steve.

Steve: "You would take your barometric pressure at sea level..."

Sea level is a good starting point.

Steve: "...your barometric pressure at the top of the structure."

The Seattle Space Needle.

Steve: "That would give you 2 pressures. You would … solve for H…difference in the two heights would give you your height utilizing the barometer and barometric pressure."

Now all of this is presented on the Mount Washington Observatory web site at weathernotebook.org. More solutions tomorrow on The Weather Notebook which is underwritten by Subaru, the beauty of all wheel drive, and supported by the National Science Foundation.