APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

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APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by APOD Robot » Thu Jul 09, 2020 4:06 am

Image Noctilucent Clouds and Comet NEOWISE

Explanation: These silvery blue waves washing over a tree-lined horizon in the eastern French Alps are noctilucent clouds. From high in planet Earth's mesosphere, they reflect sunlight in this predawn skyscape taken on July 8. This summer, the night-shining clouds are not new to the northern high-latitudes. Comet NEOWISE is though. Also known as C/2020 F3, the comet was discovered in March by the Earth-orbiting Near Earth Object Wide-field Infrared Survey Explorer (NEOWISE) satellite. It's now emerging in morning twilight only just visible to the unaided eye from a clear location above the northeastern horizon.

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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by De58te » Thu Jul 09, 2020 6:52 am

If that comet is just visible to the unaided eye than then how would anybody even know those noctilucent clouds were even there with the unaided eye?

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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by Ann » Thu Jul 09, 2020 7:47 am

De58te wrote:
Thu Jul 09, 2020 6:52 am
If that comet is just visible to the unaided eye than then how would anybody even know those noctilucent clouds were even there with the unaided eye?
Noctilucent clouds with dark clouds like letters July 5 2020.jpg
Noctilucent clouds can be really bright, and they are often very extended. I took the picture at left on July 5. As you can see, the noctilucent clouds light up the sky just as much as the streetlight lights up the ground below.

Comets, by contrast, are usually faint. Comet NEOWISE is "only just visible to the unaided eye", according to the caption of today's APOD.

Ann
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by orin stepanek » Thu Jul 09, 2020 1:21 pm

noctilucentNeowisePaoly600h.jpg


Today's APOD offers a very nice view of Neowise! :D
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by Chris Peterson » Thu Jul 09, 2020 2:10 pm

Ann wrote:
Thu Jul 09, 2020 7:47 am
De58te wrote:
Thu Jul 09, 2020 6:52 am
If that comet is just visible to the unaided eye than then how would anybody even know those noctilucent clouds were even there with the unaided eye?
Noctilucent clouds with dark clouds like letters July 5 2020.jpg
Noctilucent clouds can be really bright, and they are often very extended. I took the picture at left on July 5. As you can see, the noctilucent clouds light up the sky just as much as the streetlight lights up the ground below.

Comets, by contrast, are usually faint. Comet NEOWISE is "only just visible to the unaided eye", according to the caption of today's APOD.

Ann
If by "only just" you mean, "Oh my, what's that weird long line of light I see in the sky out my kitchen window?"
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by johnnydeep » Thu Jul 09, 2020 4:35 pm

Chris Peterson wrote:
Thu Jul 09, 2020 2:10 pm
Ann wrote:
Thu Jul 09, 2020 7:47 am
De58te wrote:
Thu Jul 09, 2020 6:52 am
If that comet is just visible to the unaided eye than then how would anybody even know those noctilucent clouds were even there with the unaided eye?
Noctilucent clouds with dark clouds like letters July 5 2020.jpg
Noctilucent clouds can be really bright, and they are often very extended. I took the picture at left on July 5. As you can see, the noctilucent clouds light up the sky just as much as the streetlight lights up the ground below.

Comets, by contrast, are usually faint. Comet NEOWISE is "only just visible to the unaided eye", according to the caption of today's APOD.

Ann
If by "only just" you mean, "Oh my, what's that weird long line of light I see in the sky out my kitchen window?"
I thought De58te might have been implying something about how the photo was taken. The comet in the APOD looks especially bright, as do the noctilucent clouds. Is this pretty much what the unaided eye would see, or do both comet and clouds look so nice and bright solely because of the photographic apparatus and whatever post-processing was done afterwards?
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by Chris Peterson » Thu Jul 09, 2020 6:54 pm

johnnydeep wrote:
Thu Jul 09, 2020 4:35 pm
Chris Peterson wrote:
Thu Jul 09, 2020 2:10 pm
Ann wrote:
Thu Jul 09, 2020 7:47 am


Noctilucent clouds with dark clouds like letters July 5 2020.jpg
Noctilucent clouds can be really bright, and they are often very extended. I took the picture at left on July 5. As you can see, the noctilucent clouds light up the sky just as much as the streetlight lights up the ground below.

Comets, by contrast, are usually faint. Comet NEOWISE is "only just visible to the unaided eye", according to the caption of today's APOD.

Ann
If by "only just" you mean, "Oh my, what's that weird long line of light I see in the sky out my kitchen window?"
I thought De58te might have been implying something about how the photo was taken. The comet in the APOD looks especially bright, as do the noctilucent clouds. Is this pretty much what the unaided eye would see, or do both comet and clouds look so nice and bright solely because of the photographic apparatus and whatever post-processing was done afterwards?
In this image, the brightness of both the clouds and the comet are enhanced over their visual appearances.
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by Boomer12k » Thu Jul 09, 2020 10:10 pm

Awesome shot...

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above the Clouds

Post by neufer » Fri Jul 10, 2020 1:31 am

Click to play embedded YouTube video.
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Re: above the Clouds

Post by MarkBour » Fri Jul 10, 2020 2:51 am

Thanks, Art (and Sean Doran). I watched this several times. Really nice. It was fun just to watch the approaching terminator, also the Plieades and then Venus (I believe) rising on the right. But the comet was truly amazing.
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Re: above the Clouds

Post by Ann » Fri Jul 10, 2020 5:00 am

MarkBour wrote:
Fri Jul 10, 2020 2:51 am
Thanks, Art (and Sean Doran). I watched this several times. Really nice. It was fun just to watch the approaching terminator, also the Plieades and then Venus (I believe) rising on the right. But the comet was truly amazing.

Indeed, great video! So the comet is (or was) in Auriga, and Venus is in Taurus, smack in the middle of the Hyades.

1 a m July 10 2020 no comet.jpg
Felt crummy yesterday and went to bed early. Woke up at 00.55 and decided to get up and check the sky. It was dark outside, with noctilucent clouds hugging the northeastern horizon.

Half past three a m July 10 2020 no comet.jpg
Went to bed again, fell asleep and woke up again at 3.15 a.m. Got up. The sky had brightened considerably, and there was a really fine display of noctilucent clouds outside. I couldn't see a comet.

Noctilucent clouds with Venus July 10 2020.jpg
Was about to go to bed again, when I just spotted a bright light clearing the rooftop of the building opposite the one I live in. It was Venus. I apologize for the terrible picture.

So there was quite a lot to see in the sky last night, but I couldn't see a comet.

Ann
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by neufer » Fri Jul 10, 2020 6:05 pm

https://earthobservatory.nasa.gov/images/146950/another-lively-season-of-night-shining-clouds wrote:
Another Lively Season
of Night-Shining Clouds

NASA, Earth Observatory, June 23, 2020

<<Every summer in the Northern Hemisphere, electric blue streaks form high in the atmosphere. These seasonal clouds typically lurk about 80 kilometers overhead in the mesosphere around the Arctic, but every once in a while they form at lower latitudes. In 2019, the clouds showed up in places where they were only rarely seen in the previous decade, including California, Colorado, and France. This year, the clouds are equally impressive.

“It‘s another incredible year,” said Lynn Harvey, an atmospheric scientist at the Laboratory for Atmospheric and Space Physics at the University of Colorado. “When noctilucent clouds extend to mid-latitudes—where people live and notice them on a daily basis—we consider that a noteworthy season.” This year’s clouds have been seen as far south as Joshua Tree, California.

Noctilucent clouds form when water vapor aggregates and freezes around specks of meteor dust floating in the mesosphere. These thin, wavy ice clouds reflect sunlight and usually shine bright blue and white. Known as “night-shining” clouds, they typically appear around dusk or dawn when the Sun is below the horizon at an angle that lights the clouds from below.

The image above shows a satellite view of noctilucent clouds on June 23, 2020. The image is centered on the North Pole and is stitched together from data acquired in several orbital passes by NASA’s Aeronomy of Ice in the Mesosphere (AIM) spacecraft. AIM’s Cloud Imaging and Particle Size (CIPS) instrument measures albedo, or the amount of light reflected back to space by the high-altitude clouds. The clouds appear in various shades of light blue to white, depending on the properties of the ice particles.

Harvey said this year’s atmospheric conditions have been outstanding for noctilucent cloud formation. The clouds largely need cold temperatures and high water vapor concentrations—both of which have been present this summer and at record-breaking levels on some days at some latitudes.

Note than on May 24, 2020, the mesosphere dropped to its coldest temperature in 14 years of records; that cold persisted into June. The mesosphere was also wetter than normal at the beginning of May, then the water vapor was likely converted to water-ice as the cloud season ensued. However, water vapor concentrations at lower altitudes (where clouds are more sparse) indicated an extremely wet atmosphere.

Harvey said the extra moisture and colder-than-normal temperatures can be traced to a few factors. First, the Sun is in a period of lower activity known as a solar minimum, so there is less ultraviolet radiation breaking up water molecules at high altitudes. Second, the mesosphere may be wetter due to air rising from lower layers of the atmosphere and carrying more moisture into the region.

“We do not yet understand whether the cold and wet conditions this year and last are due to solar influences or atmospheric circulation patterns,” said Harvey. Extremely cold and wet conditions in the mesosphere have led to abundant noctilucent clouds.

NASA Earth Observatory images by Joshua Stevens, using data from the University of Colorado Laboratory for Atmospheric and Space Physics and analysis courtesy of the MLS team and V. Lynn Harvey/CU/LASP. Story by Kasha Patel.>>
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by MarkBour » Fri Jul 10, 2020 7:19 pm

neufer wrote:
Fri Jul 10, 2020 6:05 pm
https://earthobservatory.nasa.gov/images/146950/another-lively-season-of-night-shining-clouds wrote: Harvey said this year’s atmospheric conditions have been outstanding for noctilucent cloud formation. The clouds largely need cold temperatures and high water vapor concentrations—both of which have been present this summer and at record-breaking levels on some days at some latitudes.

Note than on May 24, 2020, the mesosphere dropped to its coldest temperature in 14 years of records; that cold persisted into June. The mesosphere was also wetter than normal at the beginning of May, then the water vapor was likely converted to water-ice as the cloud season ensued. However, water vapor concentrations at lower altitudes (where clouds are more sparse) indicated an extremely wet atmosphere.

Harvey said the extra moisture and colder-than-normal temperatures can be traced to a few factors. First, the Sun is in a period of lower activity known as a solar minimum, so there is less ultraviolet radiation breaking up water molecules at high altitudes. Second, the mesosphere may be wetter due to air rising from lower layers of the atmosphere and carrying more moisture into the region.

“We do not yet understand whether the cold and wet conditions this year and last are due to solar influences or atmospheric circulation patterns,” said Harvey. Extremely cold and wet conditions in the mesosphere have led to abundant noctilucent clouds.

NASA Earth Observatory images by Joshua Stevens, using data from the University of Colorado Laboratory for Atmospheric and Space Physics and analysis courtesy of the MLS team and V. Lynn Harvey/CU/LASP. Story by Kasha Patel.>>
As I look at the graphs, I'm not really seeing the statements in the article, certainly not as a dramatic new record. The only way I can get "on May 24, 2020, the mesosphere dropped to its coldest temperature in 14 years of records" from the graphs would be to interpret that statement as "its coldest temperature *for that day* (May 24) in 14 years." Otherwise, both graphs look fairly consistent this year with other years. The only thing I can see visually from the graphs is that 2020 is the coldest in 14 years, but it is just barely colder than the other years. And the humidity graph looks totally middle-of-the-pack typical.

If I'm looking for a marker of climate change, anyway, it does not "look" like statistically significant change.
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by Chris Peterson » Fri Jul 10, 2020 7:29 pm

MarkBour wrote:
Fri Jul 10, 2020 7:19 pm
neufer wrote:
Fri Jul 10, 2020 6:05 pm
https://earthobservatory.nasa.gov/images/146950/another-lively-season-of-night-shining-clouds wrote: Harvey said this year’s atmospheric conditions have been outstanding for noctilucent cloud formation. The clouds largely need cold temperatures and high water vapor concentrations—both of which have been present this summer and at record-breaking levels on some days at some latitudes.

Note than on May 24, 2020, the mesosphere dropped to its coldest temperature in 14 years of records; that cold persisted into June. The mesosphere was also wetter than normal at the beginning of May, then the water vapor was likely converted to water-ice as the cloud season ensued. However, water vapor concentrations at lower altitudes (where clouds are more sparse) indicated an extremely wet atmosphere.

Harvey said the extra moisture and colder-than-normal temperatures can be traced to a few factors. First, the Sun is in a period of lower activity known as a solar minimum, so there is less ultraviolet radiation breaking up water molecules at high altitudes. Second, the mesosphere may be wetter due to air rising from lower layers of the atmosphere and carrying more moisture into the region.

“We do not yet understand whether the cold and wet conditions this year and last are due to solar influences or atmospheric circulation patterns,” said Harvey. Extremely cold and wet conditions in the mesosphere have led to abundant noctilucent clouds.

NASA Earth Observatory images by Joshua Stevens, using data from the University of Colorado Laboratory for Atmospheric and Space Physics and analysis courtesy of the MLS team and V. Lynn Harvey/CU/LASP. Story by Kasha Patel.>>
As I look at the graphs, I'm not really seeing the statements in the article, certainly not as a dramatic new record. The only way I can get "on May 24, 2020, the mesosphere dropped to its coldest temperature in 14 years of records" from the graphs would be to interpret that statement as "its coldest temperature *for that day* (May 24) in 14 years." Otherwise, both graphs look fairly consistent this year with other years. The only thing I can see visually from the graphs is that 2020 is the coldest in 14 years, but it is just barely colder than the other years. And the humidity graph looks totally middle-of-the-pack typical.

If I'm looking for a marker of climate change, anyway, it does not "look" like statistically significant change.
Why does it not seem statistically significant? All the graph tells us is that for the entire period the temperature was several degrees below the mean temperature of the previous years. It tells us nothing about the significance of that measurement. Depending on what you're measuring, a tenth of a degree could be very significant or 10 degrees could be meaningless.
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by MarkBour » Mon Jul 13, 2020 6:48 pm

Chris Peterson wrote:
Fri Jul 10, 2020 7:29 pm
Why does it not seem statistically significant? All the graph tells us is that for the entire period the temperature was several degrees below the mean temperature of the previous years. It tells us nothing about the significance of that measurement. Depending on what you're measuring, a tenth of a degree could be very significant or 10 degrees could be meaningless.
I think I was initially misinterpreting the statements, and they didn't seem to match the visual data, which is why I made the comment, to see if someone could set me straight (or possibly agree with me). And my very loose statement about statistical significance was part and parcel of my misinterpretation.

Having re-read them a few more times, I am seeing what they're saying. Nothing really radical, like "Wow, the coldest and wettest year on record!", more like: "The two factors that determine the abundance of noctilucent clouds were pretty good this year: It was a rather cold one, and there was also plenty of moisture."

And I don't want to criticize the wording in the article, I think I just didn't get it on first or second reading.
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Re: APOD: Noctilucent Clouds and Comet NEOWISE (2020 Jul 09)

Post by neufer » Fri Dec 25, 2020 9:03 pm

https://www.nasa.gov/feature/goddard/2020/nasa-aim-sees-first-night-shining-clouds-of-antarctic-summer-ice-noctilucent wrote:
NASA’s AIM Sees First Night-Shining Clouds of Antarctic Summer

Summer in Antarctica is marked by days in which the Sun never sets, balmy temperatures that hover as high as freezing, and electric-blue clouds of ice.
By Lina Tran, NASA’s Goddard Space Flight Center, Greenbelt, Md
Dec. 21, 2020

<<NASA’s Aeronomy of Ice in the Mesosphere mission — AIM for short — spotted the summer’s first noctilucent, or night-shining, clouds on Dec. 8, 2020. In the days that followed, the fine wisps of cloud slowly grew into slight puffs high over Antarctica. Typically, they spin like cotton candy into a mass that blankets the poles, but this season is off to a slow start, and the clouds are sparser than usual. The season is also a late one: Scientists usually expect the Antarctic ice clouds to appear sometime in mid-November and run through mid-February.

The brilliant blue and white clouds drift about 50 miles overhead in a layer of the atmosphere called the mesosphere. During summer, this region has all three ingredients the clouds need to form: extremely cold temperatures (at -215 degrees Fahrenheit, it’s the coldest part of the atmosphere), water vapor, and meteor dust.

In summer, the mesosphere is most humid, since relatively wet air circulating up from the lower atmosphere brings extra water vapor. Meteor dust comes from meteors, which are ground into dust when they plummet and burn through the atmosphere. Noctilucent clouds form when water molecules coalesce around the fine, otherworldly dust and freeze.

Also known as polar mesospheric clouds (since they tend to huddle around the North and South Poles), the clouds help scientists better understand the mesosphere. The mesosphere is where the neutral atmosphere begins transitioning to the electrically charged gases of space. From the mesosphere up, the atmosphere is in constant motion, shaped by solar activity and near-Earth space from above and the lower atmosphere below.

“Every year, we look at things that could predict when the season starts, and then we watch and try to gauge where our understanding is,” said James Russell, AIM principal investigator at Hampton University in Virginia. Some factors scientists consider are seasonal temperatures, the size of the ozone hole, atmospheric currents, and westerly winds.

Unusual weather in Antarctica led scientists to expect late-blooming noctilucent clouds. The size of the ozone hole is at a record high for this time of year. Westerly winds are gusting unusually strong. The polar vortex, which locks in frigid air over the poles, is also very large. All this amounts to a long winter, late spring, and slow start to noctilucent clouds season.

The fleeting clouds also help scientists study gravity waves, which are powerful waves of air that form when winds brush over disturbances at Earth’s surface, like mountaintops, or stir over severe weather systems like thunderstorms. Gravity waves rise through the sky, connecting the lower and upper atmosphere. Watching how they impact noctilucent clouds is one way to study how gravity waves affect the overall mesosphere. NASA’s AWE mission, which launches in 2022, will also contribute to gravity wave research and complement AIM’s observations.

It’s easy to think that gravity waves simply ripple straight up. But a study earlier this year found that the most influential gravity waves for the clouds — and that means, the upper atmosphere — might be the ones that rise like an escalator: up and across at the same time. The gravity waves that travel in this manner tend to form over tropical monsoons, then rise up from the tropics and across latitudes. The study analyzed eight seasons’ worth of noctilucent clouds, and combined observations from AIM and NASA’s TIMED mission.

When AIM launched in 2007, scientists thought they understood the relationship between noctilucent clouds and the solar cycle, the Sun’s natural 11-year cycle of activity. But the connection seems to have disappeared in early 2005. Noctilucent clouds are sensitive to both water vapor and temperature in the upper atmosphere — and the solar cycle affects both at their altitude. Yet even as the Sun progressed through its regular ups and downs, the clouds have shone at more or less the same intensity. There appears to be a delicate balance that scientists don’t yet fully understand. “Noctilucent clouds are affected by influences from above, like the Sun, but also influences from below, like gravity waves,” said Scott Bailey, AIM deputy principal investigator at Virginia Tech. “Right now, it seems like the forces from below are in control.”>>
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