Learning to read the clouds can be pugnaciously hard. At least it was for me.
I’d look at a complex sky with two or three or even four cloud types at once, and it would be hard to tell which cloud was in front of which, what was larger and what was smaller. I couldn’t visualize the underlying causes of the bewildering shapes and forms that clouds like to take. They were often breathtakingly beautiful, but I longed to know what was making them happen.
The breakthrough came during a canoe trip down the Niangua River in central Missouri. Being late summer, the river was low enough to have numerous riffles, shallow flows ten or twenty feet wide but only a few inches deep. We had to get out of the canoes and drag them to the next deep water — the bane of summer canoeing.
Often the water would be coming from two directions, and the waves would organize themselves into a rectangular pattern of ripples. They would remain completely stationary as the water flowed across the riverbed underneath them.
We stopped for a breather, and as I watched the rippling water cascading over the pebbles. I suddenly realized how similar it was to a familiar pattern of clouds that I had seen in the sky.
It occurred to me that perhaps the same principles were at work in both water and cloud.
But I wondered: The waves on the Niangua shallows were on the surface of the water, the boundary between water and air. If clouds are also waves, what “surface” are they forming on? They’re right in the middle of the air! The atmosphere is all just air, from top to bottom, right?
Wrong. As I was to learn, the atmosphere might be air top to bottom, but in between many different layers of air usually exist: warm and wet, cold and dry, dusty, clear, etc . And though you wouldn’t think so, two layers of air with very different characteristics don’t mix together easily, so they tend to remain separate. The “surface” upon which clouds form is the boundary between any two layers of air.
Water has waves, and the sky has waves. The sky is just one big ocean.
Building a Cloud
The easiest way to build a cloud is to send some “juicy” warm and humid air upwards. It doesn’t matter how you do this. Anytime air rises, it cools, because the drop in air pressure lets it expand. The expanding and cooling condenses the water vapor into droplets which can be seen, much like an iced drink on a humid day will “sweat” on the glass. A cloud is born.
In the case of the rhythmic rows of clouds as I had seen, the air is caused to rise between two layers of air flowing at different directions or speeds. The mixing at the boundary can organize itself into a wave, or rows of waves. When the front of a wave rolls downward, the air at the back is forced to flow upward — and that causes it to condense.
After my sudden insight, I began to watch the sky more with the concept of waves in mind. I found that a lot of previously puzzling behaviors and events became more understandable.
The weather is a wave
The concept of waves turns out to apply at nearly all scales.
The familiar weather map that we see with blue cold front lines and red warm fronts, is itself nothing but a wave. This might explain why these maps can bear such a resemblance to ocean waves.
This is a little different though, because rather than a wave forming between a higher and lower layer of air, it forms between two air masses side by side. Each one of these might be as large as a small continent. In this map, all the air south of the Low is part of a huge mass flowing to the right (east), and the air north of the Low is flowing left (west). The same thing happens here as happened above, with our layers of air. A wave develops as some of the southern air mass begins to flow upward to the north and the northern air wraps back around to the south. The resulting spiral or vortex is a wave, and represents where most of the weather occurs as the two different air mass mix.
A weather system is just a really big wave between two different air masses. The blue and red lines tell the boundary, where the meeting and mixing is taking place.
So next time you’re outdoors, keep an eye to the sky and see if you can spot the waves, elegant brushstrokes in nature’s way of painting.
Sunset in the Gulf of Mexico paints the sky and sea as one canvas.
Handmade greeting card, blank card or with inscription, from Skyboy Photos.