Noctilucent clouds: Ethereal, night-shining clouds
Heads up! SpaceWeather.com is reporting that, toward the end of June 2022, NASA’s AIM spacecraft detected a sharp increase in the frequency of noctilucent clouds, aka night-shining clouds. It’s the most we’ve seen in 15 years, SpaceWeather said. Atmospheric physicist Cora Randall of the University of Colorado Boulder works with AIM data and prepared the plot below. She told Spaceweather.com:
We’re speculating that the spike might be due to extra water vapor transported to higher latitudes from rocket launches. But much more quantitative analysis would be required to confirm that or not.
Tony Phillips, who writes Spaceweather.com, added:
The timing makes sense. It takes about 10 days for water vapor from rocket engines to waft up to the mesosphere. This takes us back to SpaceX’s launch of the Globalstar satellite on June 19, which caused a number of remarkable phenomena in the sky, due to the extra burn time of its 2nd-stage engine. Noctilucent clouds may be yet another byproduct of that unusual launch.
Noctilucent clouds are normally a polar phenomenon. However, since the outburst began we have received reports of NLCs from as far south as Washington State and Oregon. Look for the clouds, ripply and electric-blue, just after sunset.
Keep tabs on noctilucent clouds via SpaceWeather’s RealTime gallery, or on Facebook via the group Noctilucent Clouds Around the World.
What are noctilucent clouds?
Noctilucent clouds, or night-shining clouds, are thin clouds high up in Earth’s atmosphere – the mesosphere – as much as 50 miles (80 km) above Earth’s surface. Scientists think they’re made of ice crystals that form on fine dust particles from meteors. They can only form when temperatures are incredibly low and when there’s water available to form ice crystals.
So, why do these clouds – which require such cold temperatures – form in the summer? It’s because of the dynamics of the atmosphere. You actually get the coldest temperatures of the year near the poles in summer at that height in the mesosphere.
Here’s how it works: during summer, air close to the ground heats up and rises. Since atmospheric pressure decreases with altitude, the rising air expands. When the air expands, it also cools down. This, along with other processes in the upper atmosphere, drives the air even higher causing it to cool even more. As a result, temperatures in the mesosphere can plunge to as low as -210 degrees Fahrenheit (-134 degrees C).
In the Northern Hemisphere, the mesosphere reaches these temperatures by mid-May in most years.
We see noctilucent clouds when most of the sky has grown dark. But the rays from the sun can still reach and reflect off these eerie, ethereal clouds. They have an electric-blue appearance. When satellites or astronauts view them from space, they go by the name of polar mesospheric clouds. If you want to see them for yourself, now’s the time to look!
It’s noctilucent cloud season
The season for noctilucent clouds at northerly latitudes is now. People at high latitudes report seeing noctilucent clouds. This happens every year, from about May through August in the Northern Hemisphere, and from November through February in the Southern Hemisphere.
In recent years, northern summertime noctilucent clouds have set records for low-latitude sightings. In 2019, for example, people observed them as far south as Las Vegas (+36N) and Los Angeles (+34N). Usually, though, they’re seen from higher latitudes.
Last year, 2021, was excellent for noctilucent clouds, with many sightings over the U.K. and comparable latitudes. Spaceweather.com said that the frequent sightings in 2021 were probably due to extra water in the mesosphere.
If you want to see how the noctilucent cloud season is going this year, you can check in on sightings at the excellent Facebook page Noctilucent Clouds Around the World. (Spoiler alert: You’ll see lots of recent reports and amazing pics!)
NLC or Night Shining Clouds captured over the Moray Firth viewed from Cullen and Findochty Harbours June 6th 2022. #Scotland #nlc @NLCalerts @stvweatherwatch @BBCScotWeather pic.twitter.com/sGhDIbrNCA
— Steven Milne (@The_Cullenloon) June 6, 2022
How to see these night-shining clouds
To see noctilucent clouds, you’ll want to have certain conditions in your favor. One factor is when to look. Right about now – mid-June to July – is typically when noctilucent clouds are most widespread.
You’ll also want to be positioned as far north as possible during the Northern Hemisphere’s peak season. Canada and the UK are two locations where you’ll have a better chance to spot night-shining clouds.
Then, look west about 30 minutes after sunset. The farther north you are, the longer throughout the night you can see them. That’s because the sun doesn’t dip as far below your horizon.
Noctilucent clouds look like electric, luminous tendrils of blue-white light. They are the clouds that glow after other clouds have darkened.
What noctilucent clouds can teach us
Noctilucent clouds are sensitive to atmospheric temperatures. Therefore, they can act as a proxy for information about the wind circulation that causes these temperatures. First of all, they can tell scientists that the circulation exists. They can also tell us something about the strength of the circulation.
Scientists studying these clouds have included those from NASA’s Aeronomy of Ice in the Mesosphere (AIM) satellite. This satellite, launched in 2007, has observed noctilucent clouds using several onboard instruments to collect information such as temperature, atmospheric gases, ice crystal size and changes in the clouds. Also the amount of meteoric space dust that enters the atmosphere. You can find out what they are learning at NASA’s AIM page.
Studies have also shown that as the climate warms, noctilucent clouds become more visible.
Noctilucent clouds are like regular clouds in that they move in the sky. See the subtle movement of noctilucent clouds in the video below:
Noctilucent clouds from 2022
Check out the wave-like motion of last night's #NoctilucentClouds display in this short #timelapse (01:34 to 01:49 BST – 142 images at 2.5s exp, 155mm fl, f/5, ISO-800) #NLC #Noctilucent #NLCnow #NorthYorkshire pic.twitter.com/4vbVtc4zfo
— Steve 'Sirius' Brown – amateur astronomer ???? (@sjb_astro) June 21, 2022
Noctilucent clouds from Europe
Noctilucent clouds from around the world
Share your noctilucent cloud photos with EarthSky
Bottom line: As of late June 2022, the AIM satellite is reporting an increase in the frequency of noctilucent clouds … “most in 15 years!” Possibly due to a SpaceX launch in mid-June.
Visit SpaceWeather’s RealTime Noctilucent Cloud Gallery