Weather Blog

Alaska mountains are tall, but not *this* tall

Alaska mountains are tall, but not *this* tall
Photo of Alaska mountain range near Fairbanks, by David Ritchie, Jan. 16, 2011

Mirages get all their fame from movies and cartoons of those unfortunate people lost in the deserts who think they see a refreshing oasis, only to find it was all an atmospheric trick.

But Puget Sound area resident Darren Ritchie found on a recent trip to Alaska that you don't have to be trapped in 100-plus degree heat in the sunshine to see the something that isn't really there.

Ritchie and his family took a trip to Fairbanks to attempt to see some Northern Lights and "experience a real Alaska winter" (my kind of trip!).

I'll let his e-mail to me take over the store from here:

We’d been there before a couple of years ago but were met with cloudy skies and disappointingly “warm” temperatures in the teens above zero, so we were ready for a rematch.

This time, temps around town were generally in the -15 to -25 range and hit -30 on MLK morning, so we definitely succeeded on the first count. Interestingly, we discovered firsthand that the Fairbanks area experiences some monstrous inversions during the winter. The town itself sits in the bottom of the Tanana and Chena River valleys, where cold air tends to pool, while the hills on the outskirts of town are regularly up to 30 degrees warmer despite being only several hundred feet higher. This can give rise to some bizarre optical phenomena as light refracts through the different temperature layers.

As a case in point, on Sunday afternoon (Jan. 16), we drove out to the old Murphy Dome radar station about 20 miles northwest of downtown Fairbanks to check out the view from the top of the mountain. As we were leaving town, our car thermometer hit a low of -27 on the Tanana River near the airport, elevation 434 feet, with nearly dead calm winds. As we climbed into the hills, the temperature rose steadily. Murphy Dome is about 2,890 feet high, and the temperature at the summit was exactly zero, although there was a brutal wind at the top (probably at least 20 mph) so the wind chill was much lower. We reached the top just before sunset and hung around for a few minutes to watch the sun go down behind Denali and the Alaska Range.

I’ve attached a couple of pictures to illustrate what we saw. The first one (pic at top of story) shows Denali at center and Mt. Foraker to the right, almost obscured by sun glare. The shape of Denali is about right, although the “steps” on the left side may be exaggerated, but the mountains on the far left of the picture are more distorted. The effect became much more pronounced just after sunset, as we drove back down into town and probably got deeper into one of the air layers (below). Denali and Foraker are clearly more distorted, while the mountains to the left/east are smeared out into fantastic shapes. [He was looking south.]

I had read about mirages and specifically “fata morgana” before and knew what I was looking at, but it was still strange and interesting to see them for myself. That day, the local newspaper, the Fairbanks Daily News-Miner, happened to run a story on the subject. It just goes to show that mirages aren’t confined to hot days in the desert – you can also see them when it’s 25 below!

As to the trip itself, although we got our cold weather fix, unfortunately we didn’t quite achieve the other goal: the auroras were only dim and diffuse. I guess we’ll have to try again when the sun is more active.

---

Ritchie is right in that these mirages can occur when you have stark differences in temperatures at lower levels. Temperature affects air density and the transitions between these different densities can bounce and alter the path of light waves to where they don't travel in a straight line.

The ensuing effect is that light reflected off distant objects isn't where it's supposed to be by the time it reaches your eye, thus making for some strange sights.

That article in the Fairbanks newspaper also gives a great in-depth explanation.