Category Archives: Atmosphere

Atmospheric science, images

What’s left of Oregon

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As I drove home from the pharmacy Thursday afternoon I noticed for the first time that I could look out the windshield and see Oregon. Or at least smoke from things that had burned in Oregon.

The smoke plume from the Oregon wildfires has reached all the way to the east coast, including our little town of Rome. This is a normal view from our front porch.

This is the view Thursday afternoon.

The ridge in the distance in the first image is barely visible in the smokey image.

It’s not as noticeable in the photo as it is in real life. The smoke is thick enough that there is a distinct grayish haze in the narrow valleys on the mountain.

The US government has a web site that shows the smoke plume. The location of air quality measurement sites makes the image a little hard to see, but this is a segment of the Southeast.

The blue dot in the lower left corner is our location on the mountain outside Rome. We are just outside the heaviest part of the plume. The network news said there might be a hint of the odor of smoke, but I couldn’t detect anything.

I mentioned that I was on my way home from the pharmacy. I had been to the pharmacy to pick up some prescriptions for Leah, who is finally home after her surgery. We reported as ordered to the hospital at 7 am Monday. She didn’t make it up to her room until about 5:30 that afternoon, mainly because of lack of rooms. The surgery itself lasted a couple of hours.

When the surgeon talked to us before the surgery, he said that an MRI taken the week before showed small fractures in her hip near the lumbar region. He said the fractures were the result of osteopenia, the early stages of bone density loss that can lead to osteoporosis. I suspect that the fractures were caused by her two falls when she landed hard on her rear end. I think they added to the pain she has felt for some time.

She spent the next three nights in her hospital bed, and I did something somewhat similar to sleeping in the recliner beside that bed. On the whole, she was probably more uncomfortable than me. She was in a lot of pain from the surgery, but I think at least some of the nerve pain in her legs has been lessened. She has been on pain relievers for the nerve pain so long that she has developed a tolerance for those pain medications. That makes it that much harder to get relief.

She seemed better Thursday, and said she actually felt better. But she was still hurting enough that she went to bed early Thursday night. I am hoping the pain continues to lessen and she starts feeling better. Life has been hard for her the last few months.

Radiation fog

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We had a strong but short thunderstorm Tuesday afternoon. A cold front moved through shortly after. When I got up Wednesday morning and looked out the front, this is what I saw.

At first I thought the fog was over the river, but then I realized that the Coosa River runs on the other side of the ridge just beyond the fog. This was not advection fog, this was radiation fog.

Radiation fog forms when the ground cools on a clear, calm night, causing moisture in the air to condense into fog. On Tuesday night, there was plenty of moisture in the air because of the shower, and the skies cleared with the passage of the cold front. Perfect conditions for forming fog. The fog also defines a temperature inversion, where the surface temperature is cool and the temperature actually goes up as you go up in altitude, the reverse of the normal conditions at the surface.

I took the photo above at around 8:20. By 9:30, this is what it looked like.

The for was gone. The bright sun had warmed the surface enough to erode the inversion, and the fog had cleared.

Manmade clouds

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We live about 70 or 80 miles northwest of the Atlanta airport, as the crow or airliner flies, so we see a fair amount of air traffic. Passenger jets are usually still pretty high when they pass over us, so we often don’t see the airplane, only the contrail.

A few days ago the conditions were right for contrails.

Sometimes if the air is dry, contrails don’t last long. If there is more humidity at airliner altitude, the fine particles in a jet engine’s exhaust can become condensation nuclei for water vapor, and the contrails grow.

We can also often see smoke clouds. When people clear land they sometimes make big piles of trees that they burn (with the appropriate permit). This was a particularly big and long-lasting burn.

The smoke from this fire did not rise to any great altitude. In fact, it brushed the ground downwind from the fire. In air pollution meteorology, this is known as fumigating. If you have ever seen what we used to call a smoke stack at a factory or coal-burning power plant, you might have noticed how tall it is. That height is a result of a calculation made by the owners. The calculation yields a stack height that will prevent regulated pollutants from reaching a prohibited concentration on the ground downwind from the stack under most atmospheric conditions. The further downwind a smoke plume goes, the more it spreads out, both vertically and horizontally. As it spreads, the plume is diluted and the concentration of pollutants decreases. So, the stack must be tall enough that the plume is diluted enough that the pollutant concentration is below regulated standards before it reaches the ground.

If there is a strong temperature inversion, the atmosphere forms a kind of cap, so sometimes a smoke plume doesn’t rise very high. In that kind of case, the plume might reach the ground before it is diluted enough. That’s fumigation, and that is apparently what happened with the fire in this photo.

Of course, the smoke from this fire didn’t get ejected from a tall stack, it just rose from the fire. The heat of the fire is often enough to get the plume high into the atmosphere to prevent what happened here. Not so this time. So people downwind from this fire probably had a pretty unpleasant day.

Or, as it turned out, an unpleasant several days. I took this photo on December 20. On the morning of December 29, the day I wrote this, there was still a little smoke coming from this fire.

I asked John, our grader neighbor, if he knew what the source might be. He thought it came from a privately-owned dump, where John disposed of the trees he took when clearing our lot. The owner piles the trees and occasionally burns them.

Anyone burning large quantities of vegetation requires a different permit from the one I get when I burn limbs I collect from our yard. Depending on certain conditions that I’m not familiar with, large-scale burning might require the use of an air curtain destructor or incinerator. This equipment is supposed to contain smoke until it is burned, which is supposed to reduce or eliminate smoke. This burn apparently did not use one.

Sunset from the mall

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We went to our local mall Monday night. It was around 7:45 when we left, just in time to see the last red of sunset and the setting new moon.

I had to use my iPhone since I almost never have my camera with me. Unfortunately, for this purpose at least, the lens was far too wide to get what I wanted. I had to crop the image significantly to get this.

The brightest part of the sky also washed out the red.

Leah and I remarked on how red the sky was while we were driving back home. It made it very pretty, but the beauty belied the cause, which is dirty air. In this case, I suspect that much of what I call dirty air is really dirt, or dust, suspended in the air. It’s not particularly noticeable during the day, but when the sun’s rays have to travel through a lot of it, it tints the sky red.

We in the Southeast are under a high pressure area that tends to keep whatever happens to end up in the air suspended there. Atlanta has had air quality warnings lately, and I noticed my weather app showed one for us a couple of days ago.

We hope that a cold front that is supposed to come through next weekend will clear some of the pollution from the air, as well as bring in some slightly lower temperatures.

Twinkle, twinkle, city lights

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We can see the city lights from our front door.

They twinkle.

The video doesn’t really capture very well what the eye sees. I think the twinkling is more pronounced on cold, clear nights. That’s when there is a lot of variation in the air temperature, which can cause twinkling at the air moves around. Windy nights might be good as well, but we haven’t had a windy night without rain and fog, so the lights haven’t been visible then.

I have read that stars twinkle but that planets do not, unless they are visible near the horizon. The reason is that stars are point-sources, while planets are not. The light from a star appears to twinkle because of atmospheric refraction of the light. The refraction would be constant and the light would be steady if the air were still, but the atmosphere is constantly in motion, so the light from the stars has to travel through a medium whose density constantly varies along its path. Planets are actually discs. You can see that with a telescope, but even without a telescope the width tends to suppress the effect of refraction.

This site explains the twinkling by saying that a star’s light follows a zig-zag path, but that’s not exactly accurate. If you stand next to someone and look up at the night sky, you can both see the same star, but the light that falls on your eyes follows a slightly different path from the light that falls on your friend’s eyes. When the light going to your eyes is refracted away from its path, you end up not seeing that light. However, light that was following a different path is refracted into your eyes, so it looks like it comes from a slightly different location. That makes the star seem to move very slightly in the sky, which we see as twinkling.

When I look out at the city lights, the smaller lights twinkle while the bigger, brighter lights don’t. In this case, the small lights are like stars, and the bigger lights are like planets. None of them are point sources, so you might think they wouldn’t twinkle, but their light is passing through the densest and (often) most turbulent part of the atmosphere, which is enough to make them twinkle.