Sunrise or Sunset - Gravity Waves and the Deformation Zone

 

#2529 "Sleepy Time Sky Story"
Looking west into the centre of the DZ Col and
the Maw of the Approaching Storm... 
I love the weather!

Lines in the sky always tell a story. If there are lines, the air is moving… along the isentropic surfaces. And the air is always moving...

A  Paddler's View of a  Stroke in Duckweed 

The deformation zone (DZ) is the leading edge of any circulation. They are my very favourite meteorological conceptual model. A deformation zone is created with every stroke of my paddle. Everyone can clearly see the patterns of a paddle dipped into a pool of duckweed. Those exact same lines and swirls are created with every dip of the paddle in clear water too, although there are not tracers to reveal them. 

The absence of cloud in a clear blue sky is an identical limitation even though the circulations are still occurring. That is also why I love water vapour satellite imagery. With every stroke, a DZ line encases the two companion swirls formed by the stroke of the paddle. The flow is outward from the centre of the paddle stroke… meteorologists call this the col. The fluid swirls as it diverges in both directions away from the col. 

A  Meteorologist's View of a  Stroke in Duckweed 

The deformation zone (DZ) has several stories to tell. And there are also two sides to every line just like there is two sides to every story.  A single stroke of the paddle creates one line and four swirls. Each deformation zone line is composed of a col at the centre of the stroke, joining the starting point of the two divergent confluent asymptotes. Companion swirls are found on the opposite sides of the paddle stroke. Sympathetic, paired swirls develop on the opposite sides of those confluent asymptotes as a result of the fluid flow along the confluent asymptotes. In the duckweed frame of reference, these fluid vectors do not average to zero and the canoe (or kayak) is propelled forward. To transform this paddle stroke into the weather of the atmosphere, think of the paddle as moving the warm conveyor belt as it rises along the isentropic surface headed northward.  

Deformation zones (DZ) can become your new best friend so please try to follow the explanation. Aside from gravity waves, every line in the atmosphere is indeed a deformation zone. The shape and location of every DZ must also reveal the relative intensities and location of each of the four swirls - and that tells you everything about the weather. 

All of this bears repeating.. just in case you missed it the first time. Here is another way to look at the duckweed lines and swirls. 

Since the deformation zone is the leading edge of the flow… and if this flow is moisture laden .. we can see the cloud associated with the warm moist air rising along the isentropic surface. By examining the swirls, we can also deduce which portion of the storm is aimed at our location at that moment. The cyclonic companion has a more upward and unstable flow and thus more weather. The anticyclonic companion has more downward and stable flow and less weather.

Which swirl companion is directed toward you is typically best revealed by watching the motion of the clouds on the moist side of the deformation zone - there will be more to watch and study on the cloudy side of the line. This step will also reveal the relative location of the col in our field of view. Get ready to point the fingers of your Coriolis Hand in the direction that the cloud is moving. 

If the fingers of your right hand (Northern Hemisphere Coriolis Hand) following the motion of the clouds, point to your right, then you are looking at the cyclonic companion of the warm conveyor belt. There might even be gravity waves in the cloud on the moist side of the deformation zone angled downwind with the stronger flow along the DZ. Your fingers following that flow on the moist side of the DZ will have your Coriolis Thumb pointed upward in the direction of the rising air. Turning your Coriolis Fingers to point in the direction of the dry air on the paired side of the DZ, will have your Coriolis Thumb pointing downward. 

A similar discussion applies if the cloud is moving to the left along the moist side of the deformation zone - but you will be looking at the anticyclonic companion flow. Try it out. 

You can practice your Coriolis Hand on the DZ conceptual model. Point your right thumb upward at any cyclonic X to determine the sense of the atmospheric swirl. Point your right thumb downward to do the same at any anticyclonic N. The companion swirls are actually parts of a three dimensional ring. The paddle analogy can be replaced by the smoke ring. That science was described in "What do Smoke Rings have to do with Croquet?" as well as numerous other places in my Art and Science Blogs. 

Wind Waves Superimposed on Swells

Wind gravity waves in the clouds can also reveal the direction of the flow in a painting such as that above when animation is not possible. Locally stronger winds will be found along the confluent asymptotes. As described in the previous Blog "Seeing Even More Gravity Wave Clouds", the wind gravity waves generated by stronger winds, must also have a longer wavelength. This will cause the wind gravity waves to appear to twist downwind along the deformation zone or embedded  within the swells. 

#2529 "Sleepy Time Sky Story"
Further Practice available on the Painting
Reality can be more complicated than my graphics

I have been asked “Why Bother explaining this stuff? You have been retired a decade.” My simple answer is that nature, weather and climate are vital and if these explanations can excite just one person to pause and gaze up at the clouds or perhaps look at art, then the effort is worthwhile. The laws of nature are also something I can cling too in this modern world - nature makes sense.  Finally, some of this information was never published and I feel it is valuable science. 

Keep you paddle in the water and warmest regards... 

Phil the Forecaster Chadwick