Tuesday, March 24, 2020

Isentropic Surfaces - Science and Art Merges

#2065 "Summer Cirrus" Pixels Link
My first exposure to meteorology after nuclear physics was in terms of isobaric surfaces. Upper air charts and analyses of the atmospheric were all completed in the world of pressure. Aviation revolved around pressure surfaces and that encouraged meteorologists to do the same. Like the earthly view of the solar system and the universe, mankind first tried to make sense of everything else by placing themselves at the centre of it all.
The atmosphere does not work like that as I described in my very first post “Cloud Shapes and Lines in the Atmosphere”. The motion of air in the atmospheric frame of reference may be even further refined.

Like man, air parcels prefer the easy route that does not require spending any energy. Entropy is a thermodynamic quantity representing the amount of energy in a system (that is no longer available for doing mechanical work). For a parcel of air, entropy is a function of the air temperature, pressure and composition (water vapour, water, or ice).  The potential temperature of an air parcel is a conservative property as long as the entropy of the parcel does not change.  An isentropic chart shows these surfaces of constant entropy. Air parcels can move anywhere along these surfaces for free. I should have started my meteorological training on isentropic charts which are much more in the atmospheric frame of reference. It took me a while to figure this out…

The following graphic is a cross-section of the isentropic surfaces from Texas northward to South Dakota. The blue isentropic lines generally slope upward to the north. Of course weather is more complicated than this but simple truths are a good place to start. 

The pressure axis on the left gives a sense of height and those light grey lines are horizontal on the chart and approximately so in nature. The distance scale is on the bottom. Isentropic surfaces slope upwards towards cold air (when looking along a constant height or constant pressure surface). Alternatively, isentropic surfaces slant downward to the warmest air. Air parcels are restricted to move along these isentropic surfaces in the absence of latent heat release due to phase changes of water. The vertical motion of an air parcel can be easily diagnosed from its motion along the isentropic surface and as a meteorologist, this is something you really want to know.
Conveyor Belt Conceptual Model
Weather gets simpler when one applies these simple isentropic ideas to the Conveyor Belt Conceptual Model. Weather is much more of a creative ballet with this trio of air flow dancers than a battle. The WCB, DCB and CCB play a part in every weather system and I will introduce these cast members soon. My ongoing thanks to the COMET program for their support and encouragement!

Weather can be really beautiful. This is where I have been heading all along! Art and science merges.

Warmest regards,
Phil the Forecaster Chadwick

Tuesday, March 17, 2020

Blue Sky Blues

#1260 “Three Degrees” Pixels Link
Having introduced deformation zones, it is important to talk about those other lines in the sky. These non-deformation zone lines are completely unnatural. I called this post "Blue Sky Blues" but I could have called it "The Three Degrees of Aircraft Pollution". I thought about this post decades ago but it came to the forefront in 2012  as I painted number 1260 in my artistic journey. I was standing on the Singleton shore and the idea of "Three Degrees" came to me as I painted. That title might sound cryptic. Let me explain.
#1260 “Three Degrees” Laying in the composition
All air traffic was grounded over North America for three or four days after the terror attacks of 911 on September 11th, 2001. I was canoeing at the Frost Centre at the time. My wife and I did notice something unusual - it was really quiet and there were no planes in the sky.

 A couple of curious meteorologists investigated the impact of grounding those aircraft. They discovered that the skies were much clearer and that temperatures responded correspondingly. The most noticeable direct effect was that night time temperatures under clear skies dropped on average three (maybe four) degrees Fahrenheit below the averages established prior to 911. The infra-red radiation from the ground on those nights was not intercepted by the jet contrails and returned to earth. Simply, the nights were clearer and cooler with no air traffic and no contrail pollution. Here is the title of that research “Impact of unusually clear weather on United States daily temperature range following 9/11/2001" by Adam J. Kalkstein*, Robert C. Balling Jr of the Department of Geography, Arizona State University, Tempe, Arizona 85287-0104, USA.

There was a follow-up article that claimed that the investigators did not correctly include the effects of a warm-front in their calculations. That may or may not be the case but any reasonable observer cannot deny the impacts of pollution. Corporations that profit from the burning of fossil fuels spend millions (typically about $201 million every year) to delay and block policies to tackle climate change. The goal is to discredit research that studies the impacts of greenhouse gases and climate change. Confuse, complicate and contradict the basic science that has been well known since the 1820’s. These despicable tactics are sadly quite effective and encourage inaction and ongoing profiteering. An informed and knowledgeable populace is the solution and the thrust of these ongoing efforts. 
Still composing with a fresh contrail being laid down.
Anthropogenic contrails are man-made cirrus cloud formed when water vapour from the exhaust of a jet engine condenses on particles which can come from either the surrounding atmosphere or the effluent itself. The aircraft soot from combustion is comprised of tiny particles which make for efficient condensation nuclei. The water vapour freezes into ice crystals on the soot leaving a visible trail behind the aircraft. 

Any linear “veil clouds” that last more than 10 minutes behind the aircraft are called “persistent contrails”. These long lasting bands of ice crystals diffuse outward with time and have become better known as “contrail cirrus” being indistinguishable from naturally produced ice cloud. In fact the lines can spread into sheets composed of sub visible ice crystals that make the sky appear more grey. These blankets of ice crystals interfere with the escape of infra-red radiation from the earth surface. The distortion of this radiation balance generates a net warming at the surface. 

Scientists have been experimenting with artificial clouds for decades. Indeed weather modification has been attempted since the first time rain fell on somebody’s parade. The seeding of individual clouds to encourage convective rain or to reduce the size of hail can have impact but the requirements in energy and material to do so are typically prohibitive. Meanwhile the climate engineering experiment of global warming has been underway since the industrial revolution first spewed fossil fuel exhaust into the atmosphere in 1760. The accumulated pollution over the years has changed the globe. 

Relatively cheap, fast and generally safe air travel continues to increase by about 4 to 6 percent a year. Market factors can influence this but contrails are certainly increasing and I witness that fact in the skies that I paint. The International Civil Aviation Organization (ICAO) is a United Nations (UN) specialized agency established in 1944 to manage the administration and governance of the Convention on International Civil Aviation. The ICAO Annual Report for 2014 included the following graphic which shows air traffic increasing at about 6% a year. 
ICAO Report 2014
There is a price to be paid for this high level atmospheric pollution. Unless we act, that expense will be felt by and paid for by future generations. Shame.

Contrails influence more than just the colour of the sky and the lives of sky gazers like astronomers, meteorologists and artists. Solar power generation and agriculture feel the impacts immediately.
A typical contrail filled sky drops my solar generation by about 10 percent – which is en par with other solar power studies completed around the globe. 

Agricultural research has measured the “one percent rule”. Crops and vegetation respond to a one percent increase or decrease of solar radiation with an equal impact on growth and productivity. A study in Holland has measured this relationship as being between 0.5 and 1.0 with most results skewed toward 1.0. 

Most flights are during the day when solar power is generated and plants rely on photosynthesis. Contrails quietly threaten a staggering impact on the green circular economy. 
Nasa EOSDIS France 29 December 2019 Typical Contrails
Peter Bosman, a friend in the Netherlands has been studying the impacts of contrails and has prepared a documentary on the topic. A preview of his work is available here (https://vimeo.com/396514411). Using EODIS Nasa Data, Peter found that 50% of the days in the past four years had contrails while about 30-35 days per year had extreme contrail coverage. 

As I watch and try to better understand the skies and the weather, I continue to be disappointed at how much cloud is actually man-made pollution. Jet contrails account for a large percentage of the ice crystals in the upper atmosphere. What should be blue skies with a ridge of high pressure are almost always tainted by jet contrails spreading out with the winds aloft. The blue skies become transformed into overcast thin jet cirrostratus.
Completed under Contrail Skies on the Singleton Shore
This painting view looking westward from the shore of Singleton Lake is a typical ridge of high pressure. I think that all of the cirrus clouds in this painting are the results of jets flying in and out of Pearson International in Toronto. There were three main contrails in this particular painting when I started which contributed to the title I picked. Several jets left fresh scars on the sky while I painted. I included just one of these contrails coming from Europe along the preferred great circle route. The higher contrail cast a shadow on the lower layer of cirrostratus.

So if I am ever given the "third degree" on why I painted "Three Degrees", this will be my answer and I am sticking to it. It is a bit of science mixed with climate change and art. And it is all true.

Warmest regards,
Phil the Forecaster

Tuesday, March 10, 2020

A Closer Look at Lines in the Sky

#1538 "A longer Reach" Pixels Link
If you are lucky enough to witness a long straight line in the atmosphere, you are seeing a deformation zone. In fact every line in the atmosphere that is not a jet contrail, must be a deformation zone. Deformation zones are very common indeed!

The conceptual model of a straight line deformation zone is pictured. Together the two green arrows pointing away from the central col at "C"  along the axis of dilatation, form the deformation zone. The yellow puffs of wind blowing toward the col along the axis of contraction help to drive the rotational components of the deformation zone. This simple graphic is flat and does not reveal the three dimensional circulations that make every deformation zone line so very interesting.

As shown in the first post in this series "Cloud Shapes and Lines in the Atmosphere", the deformation zone is created by two opposing puffs of air.

In the next post "The Theory of Unified Swirls"… a puff of air was shown to create a three dimensional smoke or vorticity ring. The rotation associated with these two opposing puffs shape the linear deformation zone. A straight line deformation zone is created by perfectly balanced opposing flows which can be stationary in the earth frame of reference.

The X in the middle of the graphic represents the puff blowing into the page. Red colours are used for a upward pointing thumb and blue colours are where your thumb is pointing down. 

In the conceptual model of the deformation zone the companion rotations on either side of the inward puff along the axis of contraction are part of the same smoke ring. I would need a three-dimensional graphic to include the vorticity ring but it is important to imagine it in your mind. What happens to one companion rotation must also happen to its buddy as both are created and driven by the same puff of air.
If the puff of wind blowing into the deformation zone is stronger than the puff on the other side, the following bow-shaped deformation zone must result. The stronger puff creates a more vigourous smoke ring and the cross-section though that ring reveals faster and larger companion vortices.

A convex DZ is bowed in the direction of the stronger flow. A bowed deformation zone cannot be stationary in the earth frame but must translate in the direction of that flow. This is by far the most common shape for a deformation zone in the atmosphere. The side with the stronger wind puff is also more likely to be moist than the other. This contrast makes the deformation zone visible. Air is always going somewhere in an attempt to maintain a balance of heat and moisture around the globe. We call this weather. Perhaps an animation might make these concepts more clear.

There are deformation zones in the sky every day. Watch the cloud along the linear edge for a few minutes to determine which way it is moving. The tracer moisture will be stretched along the deformation zone in that direction. The cloud will always be stretched away from the col in the deformation zone conceptual model. By locating the col relative to your position then you can infer which part of the deformation zone is about to pass over your region.

For example, as you look toward the deformation zone line, if that cloud is moving to your right then the col is to your left. Using your right hand and directing your fingers in the direction of the cloud movement would have your thumb point upward. The red vorticity maximum is likely to cross your location. That means more weather compared to what is on the other side of the col.

Typically the deformation zone is part of the large conveyor belt conceptual model of mid latitude storms and that is where we are headed... soon but not today...

Know the wind, know the clouds and that means you will know the weather.

Phil the Forecaster

Saturday, March 7, 2020

A Closer Look at Rotational Clouds

#1908 "Cirrious Stories" Pixels Link
To better understand clouds, one just needs their right hand, your imagination and some time.

Wind shear is required to make the fastest swirls and we know that those curls must be translating in the atmospheric frame of reference. This also means they must be moving with respect to the earth. If you watch the cloud move, one can determine the direction of the wind shear in just a few minutes. Remember that moisture is required to trace the movement of the wind over time. The same movement of air occurs with or without tracer moisture. Clouds are just the integral of the motion of that moisture over time.

Now follow the cloud edge in the same direction that the clouds are moving. If you can see the entire curl, you will reach the cusp which is the end of that line. Using your right hand, align your fingers in the same way that the cloud edge curls. If your thumb point upward then that is a vorticity maximum in meteorologist jargon. If your thumb is point down then that is a vorticity minimum swirl. It is very instructive to know which when you apply the deformation zone conceptual model.  It does not matter which of the cloud edges you follow to reach the cusp at the end of the curl – both cloud edges must curl the same way.

If the moisture used as a tracer for the rotation is originally located on the outer fringe of the rotation, the point of inflection of the two cloud arcs  will be bordered by clear skies. I called this abrupt point of inflection an "outward cusp". This pattern is by far the most common and occurs frequently on the pole-ward side of the jet stream.

If the centre of rotation is actually within the moisture,  the point of inflection of the two cloud arcs  will be bordered by cloudy skies. I called this point of inflection an inward cusp.  Some drawings are worth thousands of words and will help to make this clearer.

These cloud patterns look different only because of where the moisture is being drawn from. If you mentally switch the white cloud to the blue clear sky in either of the patterns, you will achieve the other pattern. Similarly the mirror reflection of a cyclonic rotation is an anticyclonic rotation and that is how I quickly made all of my instructional graphics. Swirls really are that simple whether you call them rotation or vorticity centres.

Looking back to the early 1980's when I first started playing these mental meteorological games (mainly on midnight shifts), this all seems so simple now. At the time, it was anything but clear - the solution was very cloudy in fact ... and there was a lot of push back.

Without the support of the COMET Program and my friends in Boulder, Colorado, this research might never have extended beyond my own meteorological and artistic applications. This research is available through the COMET program around the world for free through enjoyable, entertaining and interactive on-line training sessions. http://www.comet.ucar.edu/

The Satellite Palette Flash Screen circa 2005
For me it was a fusion of science and art and I branded these sessions as the “Satellite Palette”. The colours on my artistic palette were replaced by the conceptual models that could be creatively applied to any weather situation to better understand and solve the forecast problem of the day.

In the next post we will revisit the all important line in the sky. The deformation zone was described in terms of a decrease of the wind in the very first post "Cloud Shapes and Lines in the Atmosphere".
The deformation zone can also be diagnosed in terms of the four swirls that shape that line.

Warmest regards,
Phil the Forecaster

Tuesday, March 3, 2020

The Theory of Unified Swirls

#1717 "Sunset Waves Nite" Pixels Link
Every profession has its own jargon but I will try to refrain from the practice. Swirls are call vorticity by meteorologists. A swirl is simply a rotation. In the second post of this series I explained that Rotation is the Key to Unlock Cloud Shapes. In the third post Cloud Shapes from Rotation, I described how cyclonic rotation shapes clouds. The moisture patterns that result tell you about the nature of the swirl itself.

Everything is simpler from the atmospheric point of view.  We may not live in the clouds and the atmospheric frame of reference but we can imagine. I am about to make cloud swirls and shapes even simpler and the answer was blowing in the wind all of the time. I hinted at the meaning of life in the very first post Cloud Shapes and Lines in the Atmosphere and to some, what follows may be life changing. You will be able to view clouds from both sides now just like Joni (Mitchell).

I will credit Bob Dylan with this discovery even though he was just blowing smoke. Here Bob is blowing a substandard smoke ring but it is the thought that counts.
Smoke rings are created from a quick puff of wind, near circular lips and some tracer to reveal the resultant air circulations. I am not a smoker so have never done this first hand. The puff of wind creates speed shear. Speed shear must move in the earth frame of reference which is why smoke rings are never stationary. In a flat display, meteorologists could analyze a smoke ring cross-section as follows below.

Looking in the direction of the puff, the speed shear must create a cyclonic swirl to the left and a complimentary, companion anticyclonic swirl to the right. Cyclonic rotation is associated with upward motion in the atmosphere. Anticyclonic rotation is a downer. The illustrated right hand rule will help you remember up and down. Meteorologists have treated cyclonic and anticyclonic swirls as different entities. They are not. Let me explain...

First let’s talk about the atmosphere. The atmosphere as pictured is relatively shallow. The atmosphere has a thickness comparable to the skin of an apple - more or less. Actually 99% of the atmosphere is found within 30 km of the earth’s surface. The earth’s radius is about 6400 km so the atmospheric layer is only 0.5% of the earth’s radius. That’s shallow! 

Early meteorologists concentrated on the horizontal motions in the atmosphere. Our observations were only from the surface. The paper weather maps were flat. That is all we had. How can anything so flat have any important three dimensional patterns? These concepts have led to the separation between cyclonic and anticyclonic swirls. In fact,the interesting part of weather and meteorology occurs in the vertical and we can learn from that smoke ring.

A smoke ring is simply a puff of wind and it is a three dimensional circle of spin. If we look along the same direction as the puff of wind and follow the smoke ring with our right thumb we see that both cyclonic and anticyclonic spin can be found along the same smoke ring. Meteorological convention has just separated this single, simple physical phenomena into two separate branches through only considering the horizontal cross-section. The smoke or moisture patterns across the ring are mirror reflections of each other. The smoker has learned to concentrate the smoke into tightly wound vortices.  All one needs is a puff of breath and practice.

The smoke ring and swirls are larger and stronger with a stronger increase in the speed of the puff. As the vorticity maximum or swirl to the left of the straight line puff increases, the vorticity minimum must also increase correspondingly. I called these companion circulations – what happens to one swirl must also happen to its buddy swirl. Swirls also need closure – either back on itself or on a surface. That’s just the way it is… more on this in another post.

The take home message is to remember the smoke ring in the atmospheric frame of reference. Always envision a three dimensional ring even though the flat paper might can only depict cyclonic and anticyclonic swirls. To really understand the atmosphere we need to remain in the three dimensional atmospheric frame. In the atmospheric frame, everything is much simpler to understand. A smoke ring is just one half of the deformation zone conceptual model illustrated in the very first post Cloud Shapes and Lines in the Atmosphere.
And that is how you can make a line out of rotation....

In 1985 when I started teaching this in the Training Branch of Environment Canada, I tried different approaches and diverse graphics to try to connect with the students. Everyone learns differently. I may have failed but I never gave up. Sooner or later, one of these attempts would work and open the atmospheric world to them.

I spent a lot of time thinking about and painting clouds to come up with these simple truths. Sometimes the simplest things are the hardest to imagine. Maybe I was trying too hard and over-complicating things. Maybe I was just slow…

There is more to come...

Phil the Forecaster

Thursday, February 27, 2020

Cloud Shapes from Rotation

#18128 "Just Another November Sunset" Pixels Link
In "Rotation is the Key to Unlock Cloud Shapes" streamline curvature rotation was created in the atmospheric frame of reference. How this rotation was viewed from the earth frame was studied at ever decreasing speeds of translation. The atmospheric frame and earth frame become identical when  the atmosphere frame stopped. What does all of this mean to cloud shapes?

Surprisingly meteorologists did not really understand what shaped the moisture in the atmosphere. In 1977 the thrust was into modelling of the atmosphere in the burgeoning computer age. Great strides were being made as supercomputer technology raced forward. It was very inspiring but not where my mind was... and I did not have access to those computers.

I was more interested into applying the human computer to answer some of these very basic questions. Then along came satellite imagery … The artistic, right side of the brain was all anyone needed and I played some mental imaging games every time a cloud came by - which was very frequently. An updated analysis and diagnosis of the real, physical atmosphere was available with each new image. A meteorologist could easily understand what was really happening in the atmosphere and get the jump on any computer model and construct a better forecast. Imagine the power!

I started simply with pure rotation. All of this was completed within the atmospheric frame of reference which was described in “Why are clouds shaped the way they are?". I used water vapour imagery for reasons that I will make clear someday but not today.

The accompanying animations (if they work) are worth thousands of words in describing how cyclonic swirls shape moisture in the atmosphere. The blue arrows represent the simplified atmospheric frame streamlines or wind and the size of the arrow correlates with the relative speed of that wind. In these graphics, the letter “R” is used to locate the centre of rotation resulting solely from curvature in the flow. The letter “S”, which will come, locates the centre of rotation resulting solely from wind shear. Together, curvature and wind shear cause the moisture to spin and their combined effect results in a centre of rotation located by the letter “X” denoting cyclonic rotation. The relative font size of the "R" and "S" is related to their relative contributions to the total spin.

The red “X” is considered to be positive or cyclonic (counter-clockwise in the northern hemisphere) rotation of the atmosphere. The resultant cloud edges are actually two cyclonically curved arcs that meet smoothly at the centre of rotation. Pointing your right thumb upward at an “X” also points your fingers in the direction of the cyclonic rotation of the atmosphere.

The other type of rotation is caused by wind shear. The streamlines that create cyclonic shear rotation are straight. The speed shear alone induces the rotation. Frames of reference with speed shear must translate relative to the earth. In the accompanying graphic the area of the rotation would translate to the right at the average speed of the vectors. The centre of rotation for speed shear is adjacent to the maximum wind. Looking downstream, a vorticity maximum is to the left of the wind maximum and a vorticity minimum is to the right. 

I then added this wind shear to the pure rotation case to create a swirl and more realistic patterns that compared well with what we witnessed in the satellite imagery. These patterns move with respect to the earth. I had to expand my frame of reference to include the entire storm in order to achieve a window of the atmosphere were the vector sum of all of the winds came close to zero.

Following the flow along the cyclonic arcs still meet at the centre of rotation. The point of inflection is not smooth but is a cusp when speed shear rotation is added into the mix. 

Stronger wind shear creates a more pronounced cusp and the sharpness of this cusp increases both with time and the intensity of the wind shear. The vorticity centre red "X" ends up closer to the original position of the more dominant speed shear component "S".

If one practices this just a few times, you will understand cyclonic cloud shapes. Follow the cloud edges to the curvature of the arc changes. That is your centre of rotation.

More to come...

Sunday, February 23, 2020

Rotation is the Key to Unlock Cloud Shapes

#2216 "Singleton Winter Contrails Cirrus and Deformation" Pixels Link
The meaning of life can be discovered by simply gazing at the sky. For sure there are several steps to take before we get there. My career as a weatherman all started by watching clouds and asking why? Long before I became a meteorologist. Please bear with me – we are going somewhere interesting.

The first step is to look at simple rotations in the atmosphere. In the atmospheric frame of reference, there can only be rotation. Simple rotation sculptures patterns in the atmospheric moisture and those shapes reveal the secrets of the weather.

Meteorologists have historically divided rotation into two classes – either cyclonic, that of a low pressure area or anticyclonic rotation, that of a high pressure area. When looking down at them in the northern hemisphere, cyclonic rotations spin counter-clockwise and anticyclonic rotations turn clockwise. These conventions will become much simpler and more meaningful in a few more posts but let us not rush things.

In “Cloud Shapes and Lines in the Atmosphere” I jumped right to the deformation zone conceptual model by revealing how these simple lines can form in the atmospheric frame of reference. These deformation zone lines can be understood in terms of rotation as well and that is where I am headed - but not yet. These deformation zone lines in the atmospheric frame will reveal their associated rotations. Cloud shapes and the preferred locations of clouds must follow and this leads us closer to the weather. Rotation means everything to the weather and in those truths, somewhere is hidden the meaning of life.

Cyclonic Rotations in the Atmosphere – how do they move? I will use more pictures than words in an effort to make this comprehensible.

Let’s imagine pure cyclonic rotation in the atmospheric frame of reference - the green frame on the right side of the above graphic. If we move this rotation with respect to the earth (the single purple vector in the middle above), the wind vectors that we must measure from the ground can be easily constructed - the purple frame of reference on the left in the above graphic. The "Frames of Reference Equation” goes both ways! The lines following the flow (dashed purple streamlines) look like a tough or a valley from the earth-bound view. These lines can be approximated by isobars on a surface weather map or height contours on an upper air chart. The curvature and spacing of these lines can be handled mathematically in the science of meteorology but there is no need for us to go there.

Pure rotation that is moving very quickly relative to the earth will be dominated by a strong translational vector. The trough following the winds in the earth frame will be shallow and perhaps difficult to see.

As the movement of the area of pure rotation slows in the earth frame of reference (the single and shorter purple vector in the middle above), the translational vector decreases. The vectors defining the pure rotation become a larger proportion of the total vector in the earth frame. The rotational vectors carve a deeper trough in the flow pattern following the winds in the earth frame of reference.

When the rotational speed of the vortex equals the speed of translation, a calm wind is created on the north (top of the earth frame purple graphic above) side of the cyclonic rotation. What meteorologists analyse as a low pressure centre is about to be created on the surface map in the earth frame of reference. A further decrease in the speed of translation must produce an east wind in the earth frame. This east wind invites every meteorologist to analyse a low pressure centre in the earth frame immediately to the south of that wind. You can tell from this 1977 image of a very keen and young meteorologist, that I loved finding those easterly winds and lows.
In 1977 Meteorological Technicians hand plotted hundreds of weather observations on large maps of North America complete with geopolitical lines and terrain. There was no doubt which frame of reference you were analyzing. When the map was completed, the combination of the skills of all of those involved, often created a work of art as well as science. Those are indeed pencils growing out of my ears and yes, I had many more coloured pencils in a plastic case tucked into my shirt pocket. One needed many colours to synthesize the analysis into a mental image of the atmosphere and the processes influencing the weather. Analyzing a weather map was a learning experience. Never stop learning.   
As the speed of translation of the cyclonic rotation decreases further, the low pressure centre in the earth frame shifts southward. The upper trough in the earth frame becomes deeper as the translational speed of the cyclonic rotation in the atmospheric frame decreases further.

When the pure rotation stops moving in the earth frame as depicted in the above graphic, the rotation we see in the atmospheric frame is identical to what we see in the earth frame. That upper trough transforms to a cut-off low when the translation of the rotational centre stops.

I hope you are still with me. I started presenting this material in the early eighties and have lost mostly everyone at one point or another. I have tried describing this process in many different ways hoping that one of the methods will form a connection. Once you get it, you will have it for life. 

The impacts of that rotation on cloud shapes will surprise you... but that is for the next day. 

Thank you for getting this far...

Tuesday, February 18, 2020

Cloud Shapes and Lines in the Atmosphere

"Singleton Winter Contrails Cirrus and Deformation" Pixels Link
This is the grown up version of#1533 "Long Reaching Deformation Zone". The small panel begged for a larger rendition because of the design and the meteorology. I hope that bigger is better in this case. This painting also tells the story of why clouds are shaped the way they are. It’s all in the spin that you put on the moisture. 

Cloud are born, live and die within the atmosphere. We have to view them from our fixed location on the surface of the earth. It is our only option and we see some wonderful patterns. If we want to really understand the cloud shapes though, we need to examine them from the atmospheric frame of reference. When we examine clouds from the atmospheric frame the complex patterns become much simpler.

To view the clouds from the atmospheric frame we need to move with the average motion of the clouds. Let’s consider an area of interest and average all of the winds observed from the earth’s surface to calculate the average surface observed wind within that box. Every observed wind can now be expressed as the sum of this overall average wind and a wind difference. This wind difference is the wind in the atmospheric frame of reference and it shapes the clouds. In other words the atmospheric frame of reference is an observational platform or coordinate system moving with the mean flow of the atmosphere. Some graphics might help. 
In the above graphic our simple atmosphere consists of four points. In this simplest case for the purple earth frame. These four points are all moving in the same direction and at the same speed. The average of these four identical motions is the same purple vector. In the green atmospheric frame of reference the four points are stationary. They are not moving relative to each other. The winds measured in the purple earth frame of reference are simply the addition of the mean motion of the earth frame winds plus the wind difference measured in the green atmospheric frame of reference for each of the four points. The shape of any cloud will not change if all of the points within this cloud are moving with the same velocity which must also be the average velocity for the box of atmosphere we are observing. 

In the second graphic above we have changed the winds in the atmospheric frame of reference very slightly. Two of the points in our simple four point atmosphere are approaching each other at the same speed. The average of these two atmospheric frame winds is zero so they do not change the average wind in our atmospheric box at all. If we add these atmospheric winds to the mean wind, the winds as seen in the earth frame of reference are the solid purple vectors within the purple box. Earth born meteorologists would simply observe a slight increase followed by a slight decrease in the westerly winds – if we add the points of the compass to our simple graphic (north being upward on the page). Such a minor variation in the west wind would be a challenge to observe. 

However something almost magical is revealed in the atmospheric frame of reference – a line is born in the cloud field! Any moisture within our simple atmosphere must be stretched parallel to the green double headed arrow which is the symbol for the deformation zone. The deformation zone is my favourite meteorological tool and I helped to discover the mysteries behind it. The shape of cloud line in the sky and the deformation zone can reveal everything about that portion of the atmosphere and the weather. 

The variations in the wind speed is wind shear and this causes the atmosphere to rotate like a child’s pinwheel. By convention the red “X” is considered to be positive or cyclonic (counter-clockwise in the northern hemisphere) rotation of the atmosphere. The blue “N” is considered to be negative or anti-cyclonic rotation cyclonic (clockwise in the northern hemisphere). The right hand rule makes this easy to remember. Pointing your right thumb upward at an “X” also points your fingers in the direction of the cyclonic rotation of the atmosphere. Pointing your right thumb downward at an “N” points your fingers in the direction of the anti-cyclonic rotation. 

Rotation in the atmosphere is very important to the weather but it is even more important in shaping the clouds. The mean wind in the atmosphere may move the clouds around but it is the rotation caused by subtle wind shear that really shapes the clouds. In addition and with admittedly great simplification, rising air and thus clouds are more likely located in the quadrants of the deformation zone conceptual model occupied by the red “X”. The opposite and descending cloud free air is more likely in the blue “N” quadrants. 

The observation of a line of cloud in the atmosphere can reveal the subtle relative motions within the atmosphere itself. The power of this conceptual model and the understanding of cloud shapes is remarkable. I have made a career out of unravelling these truths which were once mysteries. There is much more to come. 

There are other analogies that can be used to explain frames of reference. One can think of the atmospheric frame as a box car of a train. All of the box cars are moving at the same speed as part of the train. Simple patterns can be made within each box car through uncomplicated relative motions that are easily understood within each of the cars. Observing and explaining these motions and shapes from the siding outside the train is much more problematic and full of twist and turns. 

The take away truth is that if you really want to understand the clouds and atmospheric motions, you need to live in the same world as the clouds. The secret is to look for lines. 

I will place other simple motions within the atmospheric frame and hopefully, open the beautiful world of clouds up to you… much more to come along these lines… so to speak. 

Friday, January 17, 2020

The Birdman Chronicles

The first Bird Man Feeder (Model 2000-1) was built out of 4 inch sewer pipe. The head unscrewed and seed was poured in to fill the arms right down to the carved wooden hands. Bird Man Model 2000-1 held about 30 pounds of sunflower seed. The Bird Man swiveled with the wind so that the birds could land into the wind as they prefer to do. We had all kinds of birds visit the Bird Man! Chickadees, cardinals, crossbills, nuthatches, woodpeckers... all kinds of birds.

If you dress in the same colour of coat and stand beside the Bird Man, birds will land all over you and feed from you hand. I have even had a woodpecker feed from my hand.  The hope is that anyone who experiences the simple joy of sharing with the birds will be better able to appreciate the beauty and importance of nature. In the accompanying picture, I'm the one on the right- your right.

Sadly, Bird Man Feeder (Model 2000-1) stayed with Watershed Farm north of Hammertown on the very crest of the Oak Ridges Moraine. I am not certain what happened too him.

Plans for the 2020 rebirth of the Birdman were sparked during a Christmas walk through the Singleton forest during Christmas. A flock of friendly chickadees swooped in on us a couple of times. Once the small flock landed on my head, shoulders and outstretched hands. I wanted to feel that again and share the experience with the next generations. I also thought that I could build a better Birdman.

Birdman 2020-1 was constructed out of 3 inch pipe. I did a better job carving the hands and used worn out leather gloves to give the birds the feel of skin when they landed. The  3 inch pipe might be better for the flow of smaller seeds like niger and millet but the larger sunflower seeds really needs the four inch pipe to flow. The Birdman 2020-1 is pictured. The pants are on back order and there is still some tweaking to do.
Birdman 2020- 2 using 4 inch pipe is under construction.

The first more famous Birdman was probably Saint Francis of Assisi (1181/1182 – 3 October 1226). Saint Francis was an Italian Catholic friar, deacon and preacher. The story of Saint Francis is probably even more relevant today. Francis preached the Christian doctrine that the world was created good and beautiful by God but suffered a need for redemption because of human sin. He believed that people have a duty to protect and enjoy nature as both the stewards of God's creation and as creatures ourselves. Many of the stories that surround the life of Saint Francis say that he had a great love for animals and the environment.

There are many Saint Francis legends and some might even be true. One tells of travelling along a road where birds filled the trees on either side. Francis told his companions to "wait for me while I go to preach to my sisters the birds." The birds surrounded him perhaps intrigued by the power of his voice and apparently not one of them flew away. Saint Francis of Assisi is often portrayed with a birds flocking around him.

There is something almost mystical about bird encounters such as this. The Birdman should make it possible for a few more to feel like Saint Francis of Assisi if only for a little while.