Chinook Again

Another chinook day with very stable air. All pictures taken from the same spot 2.2 miles away.

Today: chinook

Yesterday: no chinook

Two days ago: chinook

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11 Responses to Chinook Again

  1. Colorado Wellington says:

    Tony, this observation is new to me, even after decades in Front Range.

    Atmospheric extinction and light scatter will decrease general visibility but it seems to me that this is different and it can’t be explained by cleaner air coming over the Rockies. The distortions you have shown on non-chinook days are not random as they would be just with dispersed particulate pollution. The way the light bends in specific directions in different spots at the time of the shot looks like it is caused by pockets of air of different temperature and that seems counter-intuitive to me. I would have thought that the gusts in the air compression causing warm chinook winds would create just such pockets of uneven warming but it looks like the air must be very evenly mixed—at least within the range of your shots—while pockets of uneven temperature air bend the light waves on non-chinook day.

    Very interesting. I wonder what others know about this.

    • tonyheller says:

      I have always noticed the very sharp detail of the Flatirons on some chinook days, but never documented it photographically.

      • Colorado Wellington says:

        Yes, I’ve seen that, too, but I always assumed it was simply due to cleaner air descending from the west. The surprising thing to me are the comparatively large optic distortions on the non-chinook day’s. That’s what your camera was able to show.

        • Extreme Hiatus says:

          A chinook pattern involves a large air mass pushed first higher over the mountains before falling down the other side like a big wave.

          In southwestern Alberta for example, where chinooks are often very strong and dramatic (huge temperature changes), the air goes up at the Pacific coast and right OVER the three main mountain ranges in British Columbia before falling down the east slope of the Rockies into Alberta. (Note how much narrower the western mountains are there versus Colorado).

          It is one big wind ‘uniformity’ versus the more diverse mix of local winds and/or winds originating from flat areas. That, along with its lack of moisture, is what probably causes its apparent clarity. That would be my best guess.

          • Colorado Wellington says:

            Yes, that was my best guess. A large, dry air mass moving fast down the slopes and replacing the air in the foothills that otherwise would have different thermal columns rising from an unevenly warming ground.
            I wonder how it is with the four strong winds that blow lonely and cold when the snow flies in Alberta? :-)

          • Extreme Hiatus says:

            “I wonder how it is with the four strong winds that blow lonely and cold when the snow flies in Alberta? :-)”

            Now I can’t get that song out of my head!

      • R. Shearer says:

        On a related note, the air is also dryer on the lee side of the mountains if the foehn effect is observed. A föhn or foehn is a type of dry, warm, down-slope wind that occurs in the lee (downwind side) of a mountain range.

    • R. Shearer says:

      Interesting, distortions in unstable air are from Schlieren lines dues to refraction index (temperature derived) differences (gradients). The Chinooks are apparently good at homogenizing the temperature. See the section beginning on page 5 of the following.

      Air from the West is also typically very clean. I wonder how much of an effect this has; probably quite a lot. I noticed this before on the front range but never really thought about it much.

      In Indonesia recently while diving, the Schlieren distortion underwater was intense, accompanied by alternating warm and cold currents.

      • Colorado Wellington says:

        Thanks for the Schlieren paper link. The apparent temperature homogenization during chinooks is what surprised me. The temperature rise of the compressed air during its descend is probably quite gradual and spread over much larger distances than the range of Tony’s shots.

        By the way, given the pretty good standard of science education in German schools, I was surprised how many people in Munich kept telling me that Föhn was warm because it came from the Mediterranean. I gave more credence to some people’s complaints that Föhn gives them headaches and makes them moody even though I suspected that some of them just had one too many the night before.

  2. toorightmate says:

    Well, bless my soul.
    I’m all Chinook up.

    (apologies to Elvis)

  3. SteveS says:

    Schlieren , föhn winds, chinook…much too complicated.
    Simple is best.

    I didn’t drink at all today.
    I really drank a lot yesterday.
    I didnt drink at all the day before yesterday.

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