noctilucent clouds

[mellowtigger]

The sky is changing.  Noctilucent clouds form high up in the atmosphere, about 80km/50miles upward in the 3rd layer of our atmosphere, the mesosphere. Normally, there aren't any noticeable clouds there. It previously was a rare event to see them, but they became so frequent (and at unusually low latitudes) that SpaceWeather created a whole noctilucent photo gallery for the many submitted images as this new trend became undeniable.

I didn’t know until recently, but the old adage that “warm air rises” has a very special exception. When that air includes water vapor, it’s the cold vapor that rises.

"Humid air is lighter than dry air under the same temperature and pressure conditions. This is called the vapor buoyancy effect. This study discovered this effect allows cold, humid air to rise, forming clouds and thunderstorms in Earth’s tropics. Meanwhile, warm, dry air sinks in clear skies. Earth’s atmosphere then emits more energy to space than it otherwise would without vapor buoyancy."
https://www.ucdavis.edu/news/cold-air-rises-what-means-earths-climate

I’ve never heard a convincing argument for how the Earth’s natural processes counteracted previous warm periods. It would be “interesting” if the planet formed a global high-altitude cloud barrier that reflected sunlight. That development, however, would be dangerous for what it could mean to global food supply. It seems plausible to me that increasing water vapor might be changing the content and altitude of the planet’s atmospheric layers. Clouds that used to be rare in the mesosphere are now becoming quite common.  Also, this change is squarely blamed on climate change.

"The study’s results suggest methane emissions have increased water vapor concentrations in the mesosphere by about 40 percent since the late 1800s, which has more than doubled the amount of ice that forms in the mesosphere. They conclude human activities are the main reason why noctilucent clouds are significantly more visible now than they were 150 years ago."
https://news.agu.org/press-release/climate-change-is-making-night-shining-clouds-more-visible/

It's been about a decade since I first mentioned them, so it's appropriate that this 10-year anniversary includes a special headline again from SpaceWeather today.  Remember the new rule: cold water vapor rises, and the mesosphere is very cold indeed.

A Major Outbreak Of Noctilucent Clouds
“NLCs are Earth’s highest clouds. Seeded by meteoroids, they float at the edge of space 83 km above the ground. The clouds form during summer when wisps of water vapor rise up to the mesosphere, allowing water to crystallize around specks of meteor smoke. This summer, record cold temperatures in the mesosphere are boosting their production.”
https://spaceweather.com/archive.php?view=1&day=06&month=07&year=2020

Earth's cloud coverage is growing in the high atmosphere.  That's not a good trend for food production, forest growth, algae growth, or solar energy production.  I agree wholeheartedly with Greta Thunberg that all of humanity should be angry about inaction and frantic for change.  I am.  I want big changes, and I want them to happen very fast.  Our timetable is short.

What about you?

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[mellowtigger]

And even more news since I wrote this blog.

"After snapping photos of noctilucent clouds for nearly a decade, photographer Chris Ratzlaff noted that he has had more sightings in 2020 than in past years."
https://www.earthobservatory.nasa.gov/images/146950/another-lively-season-of-night-shining-clouds