Clouds

"I've looked at clouds from both sides now"

Joni Mitchell

Lenticular clouds in Centennial, Colorado.

People have looked for images in clouds for at least as long as humanity has been recording it's activities.

I lived most of my life in the Southeast United States leaving only for a construction job in Montana, four trips to or through Denver (and the states I passed through on the way), and two seasons on a laybarge in the Gulf of Mexico. But I've seen some weather.

Every area has its distinctive weather. The reason we could predict our weather with any certainty in Alabama was that it was coming from where I live now, Colorado, and we had plenty of time to see it coming.

As each area has its characteristic weather, each has its characteristic clouds.

The massive high-topped thunderheads with anvil shaped tops are rare here. We get a lot more hail; they get a lot more tornadoes. They also get hurricanes.

We get these weird lenticular clouds like the ones in the picture above.

As air flows across the Rockies and out over the plains, it can set off standing waves, like those that form when a person blows across the top of a soda bottle. At the bottom of the waves, the air is warm and can hold moisture as invisible vapor, but when the air is carried to the top of the waves, it cools off and releases the water as cloud droplets. A person from the east might think "rain coming," but these are actually stable weather clouds, like the big fluffy cumulus clouds of the Southern summer.

Those Southern cumulus clouds could build up into far from stable cumulonimbus clouds. I had one drop a tornado into a farmer's field next to where I was driving once. I didn't usually speed. I did that time. Clouds can cause you to get excited.

I was driving near Tuskegee, Alabama on I 75 and there was this huge thunderhead over me. The bottom was flat and it looked like I could reach up and touch it. It was electric blue. There was so much water in the cloud that it piped the color of the sky above it right down to the bottom. That's the kind of cloud that can drop a tornado down right on top of you without any warning.

The funny thing is that I saw so much storm activity before I became a storm watcher about five years before my retirement and never saw sign of another tornado, not even during the disastrous outbreak of 2011.

One of the weirdest cloud formations I have ever seen were the hole-punch clouds one summer in Selma. An even sheet of clouds had big circular holes in it, all the way up to clear blue. We didn't know what caused them back then. It turns out that planes flying through clouds can cause droplets to coalesce, like when you put a drop of detergent in a bowl of greasy water.

The most beautiful display of weather I have seen was a very darkly overcast afternoon on a laybarge. There was a clear band on the horizon where the sun was setting blood red. It cast a red glow over the bottom of the clouds and there was a brilliant triple rainbow.

I've been chased up Mount Carbon three times by thunderstorms. Walking east from Morrison on the Bear Creek Trail carries you through a broad, treeless area of Bear Creek Lakes Park. With no cover behind me and no cover and a lung busting switchback before me, I heard a rumble at my back and turned to see massive black clouds boiling up over Mount Falcon. There was green-ness in them, indicating hail, which I didn't want on me, so I walked fast.

All three times I reached the shelter at Mountain View before the storm hit.

What causes cloud colors. Well, I talked about sunrise and sunset clouds in the last blog. Why are clouds white and, of all colors, dark gray? Is water gray?

We talked about Rayleigh and Mei scattering last time. Mei scattering is caused by aerosols, particles that aren't molecules but they're still small enough to stay suspended in air. And remember that Mei scattering doesn't pick and choose specific wavelengths of light like Rayleigh scattering does, so it's not surprising when clouds are white, but gray?

A few years ago, I built a Joly Photometer. It's basically two chunks of paraffin separated by aluminum foil. Here it is.

If you put a standard light source on one side and a light source of unknown brightness on the other, then move the unknown source nearer or further away until both sides of the Photometer look the same, you can calculate from the difference in distances of the light sources from the photometer how bright the unknown source is.

But notice that the two halves, which are from the same slab of wax and, therefore, the same color, look different. The apparent color is from the white light illuminating the wax. The top slab is lit by more white light ..therefore, whiter.

Clouds are the same way. Less light makes its way down through the cloud so places with less light look less white and our eyes are rigged to emphasize contrasts so, next to the bright white of the tops of the cloud, the bottom sometimes looks positively black.

Notice that the gray parts of clouds are usually a cool gray until sunset. The blue of the sky also comes through misty clouds.

If you ever visit the Great Smoky Mountains, you will see that they, indeed, do look smokey. That area has always funneled aerosols in, hardwood tree pollen, smoke, and more recently, abundant industrial pollutants and they disperse white light efficiently. Add in the sky blue and there's smoky mountains.

Green clouds are a place where light has to pass through so much dispersion that all the blue is gone. Notice that it's a sorta dirty brown, meaning that light at the red end of the spectrum is there, too . Clouds with that much water and ice in them will often mean hail. I run from those! Mother Nature doesn't want me there.

Hail forms in clouds with strong updrafts. High up in cumulonimbus clouds, water freezes into tiny ice crystals until they are too heavy to remain suspended in the air and then they start to fall, but they get caught in the updraft and are blown back up. They pick up more moisture and freeze another layer. These little balls of ice will ride winds up and down until they're no longer little balls of ice. When they finally fall to the ground, they can be destructively big balls of ice!

Cloud watching is a great pastime. You can get a good idea of what to expect of the weather in your area and, occasionally, you'll see something rare and spectacular!

What about that sky color?

There are a couple of hints as to why the sky is blue that are easy to obtain.

First, look straight up through a polarized sunglasses lens. Rotate the lens and see what happens. You'll see it lighten and darken. Second, note that the sky is not always blue. There's a definite sequence of colors as the day progresses: reds and oranges, yellows, blues, then the reverse.

What polarizes light? Reflection! When light bounces off something, it comes off organized. That's what causes glare and glare is why there are polarized sunglasses to start with.

Light is sorta complicated and maybe you don't want the excruciating details, but, at base, it's a wave (like ocean waves) made up of electric and magnetic fields. The fields move at right angles to each other. The waves can be oriented in any direction and they are when they leave the sun.

But when light hits a surface, whether it's a molecule or a lake, it's absorbed by the atoms in the surface. Some of the atoms send out light when they calm down, sometimes in a different color but often unchanged. Different materials are better at this than others. That's why metals reflect better than glass.

But the gas molecules in the atmosphere absorb and re-emit sunlight and the light they re-emit is polarized. Although molecules tend to be neutrally charged overall, most of them have different charges in different places. Remember that like charges repel so molecules next to each other tend to drive each other's electrons away from each other. So molecules tend to organize themselves. I say "tend to" because it's not a strong phenomenon and not all the molecules in air are lined up like a high school marching band. But light coming off these molecules also tends to be lined up. It's called Rayleigh scattering.

Here's a shot of the sky through a polarizing filter.

After turning the filter ninety degrees, it looks like this.

Notice the gradation of light toward the sun. There is another kind of scattering in the atmosphere. Mie scattering is from larger particles: dust and other aerosols like water droplets. A big difference between Mie and Rayleigh scattering is that Rayleigh scattering is affected by light wavelengths. The shorter wavelengths (violet, indigo, blue) are scattered more than the longer wavelengths (red, orange, yellow). Mie scattering disperses all the colors about the same. 

Space is black and the sun is almost white. As sunlight comes into our atmosphere, ultraviolet (eaten up largely by ozone in the upper atmosphere), violet, and indigo goes first. What reaches us is blue. As a spot on the Earth rotates away from the sun, light has to travel through more atmosphere to reach it. Green drops out, but you can't see much green since it's still mixed with a lot of blue. Yellow drops out, and then you get the oranges and reds of the sunset.

Keep in mind that the same sun creating beautiful sunsets over the Rockies is creating a blue California sky at the same time.

The sky closer to the sun looks whiter due to Mie scattering. So that's why the sky looks blue...and white and orange and red…

So, using color filters.

Filters have a coding system that looks rather arcane. I mentioned it in the last blog. The filter I used was a CTO ¼ 6500 to 4500 K ½ f/stop gel correction filter.

CTO stands for "color temperature orange". There are also CTB (color temperature blue) and "plus green" or "minus green" filters. CTB filters are specifically there to make tungsten light look like sunlight. They "cool down" yellowish light. CTB does the opposite. I wanted to take blue out of my picture so I needed a warmer filter. ¼ is just the strength of the color change. ¼ is a light colored filter.

The K number is color temperature. All bodies above absolute zero have molecules that vibrate - that's what heat is - vibrating molecules. And if molecules are vibrating, so are the charges within them. Moving charges are what causes magnetic fields. Moving magnetic fields create electric fields and when magnetic and electric fields start moving together, you get electromagnetic fields - light.

Relatively cool bodies like a summer sidewalk (see my blog for Friday, August 30, 2019, "Trail temperature vs. air temperature") might seem hot, but they're not hot enough to glow. But they are giving off light in the invisible, infrared range.  Infrared light is how heat is radiated because when infrared light hits matter, the matter heats up. 

As objects get hotter, they begin to glow a dull red, then orange, then yellow, then blue, and then they go white. The K number in filters stands for "Kelvin" as in "Lord Kelvin" after whom the Kelvin temperature scale, preferred by scientists, is named. The K number is the color that most closely resembles the color given off by a hot body around that temperature. A hot body from 6500 K to 4500 K will give off a yellow color. Larger numbers denote bluer colors, smaller numbers mean redder colors.

The f/stop is how much light the filter lets through. On a camera, the f-stop is the ratio of the lens' focal length to the diameter of the aperture. That might sound complicated but remember that the camera's focal length is related to its light gathering power and the larger the aperture, the more light can get in, so the smaller the f/stop number, the larger the aperture, and the more light is passed through.

An f/stop of ½ does not mean that half the light gets through. It's actually a very light filter that lets a lot of light through. An f/stop of, say, 8 would be much darker.

Correction or compensation filters tend to be pretty light. There are also color filters that are intended to really alter the color of photographs for special effects. They cut out a lot more light in specific colors. There are also neutral filters that just cut light in all wavelengths, polarizing filters, and special effects filters like diffraction gratings that give you rainbows.

Some photographic filters are made of glass or thick plastic. Gels are thin plastic films. I like them because they're inexpensive but they do the job and the thicker filters are harder to mount on my cell phone. I just slip the gel between my camera lens and the phone case and I'm ready to go.

The sky is what you have to look through to do astronomy so, if you're interested in sky watching, it behooves you to understand the weather.

Can I trust my phone? Part 2

A while back, I downloaded an app that would do spectrometry. It would split light coming into the camera into its constituent "rainbow", which is cool since that is a way to analyze a substance. Each element has a rainbow fingerprint.

I was excited! I wondered if the representations of incandescent elements on the Internet would be true enough to create a faithful spectrum, so Zi pulled up a picture of a hydrogen lamp and looked at it with the spectrometer. Hydrogen has a very well known spectrum so I knew what it was supposed to look like. 

Wow! It looked great!...except…why was all that blue there? Hydrogen isn't supposed to have that big blue spike at the left end of it's rainbow.

I took my phone outside and looked at the sky through it's camera  Wow! Blue skies smilin' at me...way too blue skies, did I see. I was blue. I dumped the app.

It wasn't the app's fault. Phone cameras are made to produce pretty pictures and bluer skies are prettier. But they're not true blue and science looks for truth.

My son suggested that I use a yellow filter to remove some of the blue coming into the camera and then use the color balance on the camera to get back to true color, and it worked! On the hydrogen spectrum, it worked, but on everything else, it removed so much blue that I couldn't put any back in. blue again!

But recently I bought a packet of Selens Flight Flash Color Strobist Lighting Gel filters. Gels are plastic films. Less expensive than glass photographic filters, they're often used as compensation filters for different light sources. Slipping the ¼ CTO 6500 to 4500 K lightly yellow correction filter over the camera lens, between the phone and it's case did a great job. I used the SnailCamera Pro app, which gives me considerable color balance control to rebalance the picture and I "eyeballed" it until it looked right.

Here's what the camera saw without the picture.

Here's what the scene actually looked like.

Okay, a caveat. The colors were right but I lost some detail. The individual stones in the chimney lost some definition, but right now I'm more concerned with color values. I think some contrast adjustment could get some, if not all, of the definition back.

But I am impressed with the light capturing abilities of modern cell phones. Here are some early evening pictures I took.

A nice sunset

The same shot after the sun had gone away.

A star. Vega. I could not have seen that with my last cellphone camera.

Cell phones offer a lot of power to record your world but know your instrument. It's primary purposes are communication and entertainment. Accurate records require some finagling.

Interlude

From the instant of its creation, the universe has been in the process of running down. It's called "entropy". To quote African writer Achinua Achebe and Irish poet William Butler Yeats, "Things fall apart." Except for some miracle - a Big Crunch or the Creator's decision that it's time to wipe the old slate clean and create a new, the inexorable March to uniformity will lead, in a few billion years, to a vast ocean of hydrogen, atoms so far separated that there will be no opportunity for them to crash together to form anything more complex.

But there is turbulence in time. Diversity feeds on itself. As long as things actively fall apart, they also fall together. There are swirls in entropy that pushes it, through sheer momentum against itself. One quality of living things is that they transform. They create order out of disorder. The inert dust and muck around us fall together, against all probability, to form...us.

Life isn't the only builder. There's also chaos. Nature decrees that matter attracts matter and, when enough gas and dust is pulled together, the crushing results begin compacting hydrogen into helium and then larger atoms, under fantastic heat, until the energy is expended. The heaviest element that can be created in a star is iron, but the death throes of a star, the nova, is incredibly energetic, crushing even more atoms together to form brilliant spectacles in the sky, destroying everything in the cosmic neighborhood, and blowing out clouds of element rich dust to settle down on the universe.

The dust we see in a sun beam is mostly the detritus of life - dead microorganisms, and in our homes, skin cells sloughed off our own bodies and the tiny creatures that eat them. But a significant portion is micrometeorites, much of it, that fine dust blown out by dying stars. Over millions of years it has settled on Earth along with the usual products of erosion and, in the molten mix of tectonic plates, heavy elements concentrate in globs of magma to be extruded in cracks near (in geological terms) the surface where it can cool into rich veins of ore.

It might have happened in the crash of two such plates in the Earth's crust that buckled, what would be North America, thousands of feet upward to form the Colorado plateau. Or maybe before. That wasn't the first time the crust had been buckled around here. The Appalachians once rivaled the Himalayas in grandeur but, over time, they were worn down to the narrow band of mountains they are today. The Ozarks had their time.

But time has been working on the Wild West, too, eroding the smooth skyland of Colorado into deep ravines between towering mountains, dissolving ore veins into acidic, carbon dioxide rich lakes (the product of acid rains and dying organisms) where lead precipitated out into insoluble lead carbonate, cerussite, carrying other heavy elements with it, including silver. 

Nature values nothing. She just acts. But the new (in geological terms) animal invading the continent of North America brought a brain that valued much, especially that which is rare and that which glitters...and silver is both rare and glittery. Those that came from the east recognized the white sands below the highest mountain of the North American Rockies, Mount Elbert, to be composed of cerussite and understood that it often carries silver.

When that was confirmed, the new town of Leadville, Colorado, founded in 1860, began attracting miners and miners attracted other civilized creatures like the faro dealing Doc Holliday, fellow Georgian turned Coloradan (he's now buried in Glenwood Springs), and the unsinkable Molly Brown...

and myself. Yesterday, two friends and I, taking a break from stargazing and pendulum watching, traveled to this interesting little village below Mount Elbert to look at saloons and city halls preserved for posterity and tiny homes. And here are some pictures.

Mine dumps and mountains

The Old Church on Harrison Avenue and Mount Elbert.

Lake in the mountains

My personal transportation for several years has been the trains and buses around Denver but with Covid-19, I've avoided them since they require a mask and it's hard for me to get enough air through a mask.

I still walk to the shops in the area. There are always interesting things on the way.

One of my favorite wildflowers, the common milkweed, is blooming now.

Purple seems to be in vogue. This is Colorado and thistles are everywhere.

These rare gems are a variation of the Mallows that are everywhere. They're called "cowboy's delight" or "copper Mallows." It's strange to think of them so closely related to hollyhock, hibiscus, and marsh mallow (yes, marshmallows were originally a plant product, made by whipping up the thick, starchy solution from marsh mallow roots.)

We've been having moist air coming over the Rockies, giving us occasional rain storms to cool off our afternoons.

The public library has been closed for remodeling and now, with Covid 19, will it ever open? Stay tuned.

Much of our weather has a lot to do with the jet stream that shifts like an injured snake over us and the Rocky Mountains to the west. I've flown over the Rockies in a jet and from up there, they don't look quite so big and, after all, what's 14,000 foot mountains when the atmosphere is well over a million feet thick.

But when a tsunami is far out at sea, you can only measure a small change in the surface of the ocean. It's only when the depth changes that the sea turns into a great wall of water.

When air masses flow over the mountains and then out over the plains, they can set up vibrations. As the moist air moves upward, it cools off and water condenses out in the form of clouds. The air at the bottom of the waves is clear.  We get interesting rows or hatches of clouds. Sometimes, they're said to look like UFOs. Technically, they're called "lenticular clouds" for their resemblance to lenses.

Little Dry Creek is up now. It's not a mountain Creek, so it's not from snow melt. It's being fed by the afternoon showers and there seems to be a lag time between the rain and the rise in water level. I'll have to check that out sometime.

All walks are interesting. If you stay aware of your surroundings, there will be plenty to engage you.