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.