Pop Goes the Weather Balloon

June 24, 2008 at 8:50 pm | Posted in Uncategorized | Leave a comment

Every morning and every evening, the National Weather Service office in north Fort Worth sends up a weather balloon, carrying instruments to measure the temperature, humidity and pressure as it rises through the atmosphere.  And by tracking the motion of the balloon, they can also deduce the winds in the upper atmosphere.  This is a vital service, since the atmosphere is three-dimensional.  Just knowing what’s happening at ground level isn’t good enough.  We really need to also know the state of the atmosphere miles over our head in order to have the best chance to come up with an accurate forecast.

Sometimes, we take those twice daily weather balloon launches for granted.  But something happened this evening that really made me think.  The NWS noted that the balloon made it up over 100,000 feet and it was still almost directly overhead!  Usually strong upper level winds will sweep a ballon miles away before it reaches that height.  They even mentioned that just before 8pm, they could still make out the balloon with the naked eye, almost an hour after its launch.

In fact, as the ballon rose, and expanded (due to the much lower atmospheric pressure outside of the balloon) it reached an altitude of 105,000 feet before the balloon popped.  At that height the atmospheric pressure was  only 9.18 millibars.  Normal pressure at the surface is 1013.5 millibars.  There’s not much air up there above 100,000 feet.

An interesting thought occurred to me.  The Phoenix lander, which touched down in the arctic regions of Mars is reporting surface pressures of 8.55 millibars.  That’s very close to what we see on earth at 105,000 feet.  If you want to learn more about the current status of the Phoenix spacecraft, check out this link to The Planetary Society and to the University of Arizona:

http://planetary.org/blog/

http://uanews.org/node/19883:

Chief Meteorologist David Finfrock

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