Classic clouds #1 – Kelvin-Helmholtz billows

My last few posts have been about fairly meaty climate issues or on science policy.  These are important subjects but one of the things I love about atmospheric science is that there are some beautiful things in our skies.  This post is about one of my personal favourites, Kelvin-Helmholtz Billows:

These billows occur when a layer of cloud is found beneath a layer of warmer air and the two layers are flowing in different directions. When this situation occurs, the lower cloud layer is not bouyant so it can’t push up into the warm layer.  However, under the rare circumstances that the two layers are flowing just right, the interaction between the two layers will form an instability and the cloud layer will “break” into the upper layer in the wave-like pattern seen above.  These cloud formations are so rare that they rank as the highest scoring cloud in the Cloud Appreciation Society’s Cloud Collector’s Handbook.  (Confession: I have never actually seen one in the sky.)

But, I have seen one in the lab!  The amazing video below shows an experiment I did during a summer school at the University of Cambridge where the same conditions can be set up.  Enjoy.

[Thanks to Tor Smith (University of Leeds) for the footage and to the University of Cambridge Fluid Dynamics labs for the equipment.]

There are some nice observations of these cloud using the Chilbolton radar either in Chapman and Browning (1997) or on this University of Reading webpage.

UPDATE: I recently saw something that looked like KH billows in the sky where I live. They formed on an aeroplane contrail so maybe this pattern was formed more by turbulence from the plane than atmospheric shear that was already there. Either way, it made my day!

Reference:

ResearchBlogging.orgChapman, D., & Browning, K. (1997). Radar observations of wind-shear splitting within evolving atmospheric kelvin-helmholtz billows Quarterly Journal of the Royal Meteorological Society, 123 (541), 1433-1439 DOI: 10.1002/qj.49712354114

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5 Responses to “Classic clouds #1 – Kelvin-Helmholtz billows”

  1. Classic clouds #2 – virga « Our Clouded Hills Says:

    […] Classic clouds #2 – virga By andyrussell This is the second in a series of posts covering my favourite clouds.  The first post looked at Kelvin-Helmholtz billows. […]

  2. alan Says:

    These “Kelvin-Helmholtz” formations are caused by GeoEngineering . This article is propaganda for the GeoEngineering agenda. Don’t believe the lies, believe your own eyes. Look up to the sky, it used to be blue and not a white toxic haze. And yes, there are real contrails from airplanes, and then there are real aerosols being sprayed that are causing dire consequences. Do the research yourself!!!!

  3. Serano Says:

    Wikipedia is bullshit! They are just talking about contrails not chemtrails. They avoid to recognize existing of chemtrails.
    [I think that the wikipedia page on the “Chemtrail conspiracy theory” is not too bad and not only about contrails as you claim – AR]

    That’s geoengineering in action. Watch these movies and think…
    1.http://youtu.be/jf0khstYDLA [Wow – over 90mins and the 15mins I got through said almost nothing! – AR]
    2.http://youtu.be/x9VcWkFrXWY [I didn’t even open this one, I lost confidence in your recommendations with the first one – AR]

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