December 13, 2013

Giant Towers over the Olympic Mountains

During the past week I received a startling picture from Andrew Laszlo, a doctoral candidate in the UW Physics Dept.   Andrew had been hiking in the North Cascades and took the following picture of the Olympic Mountains at 11:25 AM, December 8th.  Huge towers, resembling mesa, loomed high in the sky, well above the usual position of the Olympic peaks.

Had the mountains grown suddenly?  Rapid uplift?   A photoshop moment?

No, this was a wonderful example of a superior mirage, when the atmosphere acts as a weird lens that causes objects to appear bigger and higher than they should be.  Let's investigate.

First, the facts.  The following map shows the location of Andrew when he took the picture.  He reported being at 6900 ft at the time.

Light can be bent in strange ways when there are very large changes of temperature in the vertical.  We can get an idea of the temperature structure at the time from reports from planes taking off and landing at Seattle;  some are equipped with weather sensors.   Courtesy of UW's Mark Albright here are the temperatures from an aircraft taking off from Sea-Tac Airport at 11:36 AM (1936 UTC) Dec. 8.

If you look closely you will see a strong inversion between  5722 ft and 6932 ft (from -11.1 to -7.7C), an inversion right below Andrew's location when he took the picture.  Confirmation of the inversion came from the radiosonde sounding at Quillayute, on the WA coast.  The sounding was for approximately 4 AM

Temperature is in red. You see how the temperature warmed abruptly below around 780 hPa pressure (about 6900 ft). 

When you have cold air below, with warmer air above, separated by a sharp inversion, the abrupt change in atmospheric density that results can produce a lens effect that makes object loom upwards.   As noted above, this is called a superior mirage, and is illustrated in the two schematics below.

This phenomenon is also known as the Fata Morgana, named after the illusions produced byKing Arrthur's enchantress half sister. 

 Finally, I should note that others have observed this phenomenon before around the Olympics.   Here is a picture of the Olympic Mts. I found taken from Vesper Peak in the North Cascades on Dec. 3, 2011.  The picture was taken around 12:30 PM at around 6200 ft.

Picture courtesy of Steph Abegg

What did the radiosonde sounding look like at Quillayute that afternoon?  Here is it (for 4 PM).   850 hPa is about 5000 ft and the two black lines are temperature (right one) and dew point.  Another strong inversion below the photographer's location!  Further support of the inversion causing the superior mirage of the Olympics when viewed from altitude in the North Cascades.

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  1. Quite amazing, the way the shapes of the mountains were altered in that photo. I've been looking at the Olympics for years, but never saw the flat top distortion like that.

    Regarding the last blog and your KPLU talk today, Cliff, I do hope we don't have to pay for this high with a cloudy wet spring. I like to see the good weather when the sun is high in the sky and the weather warm. I actually wouldn't mind some storms now... is the jet stream north of us, or is it south of us?

  2. Nice to see a Steph Abegg photo in your the blog! Her pictures are amaging, and your blog is excellent too!

  3. This is why I keep up with your blog. Always least to the layman. Thank you for what you do.

  4. So, can this illusion or mirage effect take place over the ocean? Last week, 2 of my co-workers and myself saw what appeared to be crazy massive waves out in the ocean about 10 miles from shore, and yet the water near the shore was very calm. The waves looked massive and roiling. Wondered if this same principle applied here.????

  5. I will only consider purchasing if it contains a picture of Jim Foreman atop the Space needle in storm force winds and blinding snow!!!!

  6. You should send that to Astronomy Picture of the Day (NASA)

  7. Dear Cliff,

    I help with ski programs for Seattle Schools and teach middle school kids on Snoqualmie Pass.

    I am freaking out! Where'e the snow and what's your guess when it might arrive?

    Skier Jay

  8. This happened to me on Saturday afternoon, with Rainer appearing bold as brass before me as I drove doe 405. Nice to have some idea why!


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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