Atmospheric conditions show pilots what to expect aloft

It is a cold winter day in Fairbanks, Alaska. But some places are not as cold as others.

Temperature inversion over Fairbanks creates vivid optical effects, transforming distant mountains into greatly distorted features. Photo by Carol Lee Gho

The front page picture on the November 28th edition of the Fairbanks Daily News Miner gives a dramatic view of what is happening. A temperature inversion is holding a layer of cold in the valley bottoms, with temperatures as low as -26 degrees F. At the same time in the hills behind Fairbanks, the thermometer registers as high as +8 degrees F.

The change in air density marking the boundary of the inversion distorts the peaks of the Alaska Range, located 90 miles south of Fairbanks. Under these conditions, the normally sharp skyline– with peaks pushing above 14,000 feet– looks more like mesa’s of the south western US.

Map of surface temperatures observations show conditions as cold as -26 deg. F in valley bottoms, where hill tops register as much as +8 deg F.

During these events, local pilots know that even though it is cold at the airport, once above the surface, they can expect to be flying in warmer air. If one looks at the horizon during the climb-out, it is not uncommon to see the skyline flip-flop wildly while crossing through this boundary until solidly into the warmer air above.

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About Tom George

Tom George serves as the Aircraft Owners and Pilots Association’s Regional Manager for Alaska. He resides in Fairbanks, and flies a Cessna 185. Follow Alaska aviation activities and events on Twitter at http://www.twitter/AOPAAlaska or at:
  • Doug Braddock

    Keep in mind that the warmer air aloft during inversion conditions contains more moisture than does the cold air at the surface. This can cause an abrupt fogging/icing of the aircraft windscreen and windows on climb out. While not enough to affect aircraft performance, this frost can take awhile to go away, even with the defroster going full-blast. The first time this happened it really took me by surprise and I was glad I had just received my instrument rating!

  • Steve Walton

    I was a bush pilot in the mid 60s and learned quickly how an
    inversion layer affects your aircraft. On takeoff when the ground temp was
    -40 as soon as you got to about 300 feet the windshied would become entirly
    fogged over, It was quite a shock if you weren’t aware that could happen. Of
    course it didn’t last long as you continued to climbout.