What are Noctilucent clouds?

2023-07-12
What are Noctilucent clouds?

Summer is a time of interesting atmospheric and cosmic phenomena. Mainly because the weather is nice then and we can enjoy cloudless skies more often. However, clouds are not always a bad thing for astronomical observations. They themselves can also be extremely interesting and give us great views. The season for noctilucent clouds - some of the most interesting clouds we can admire from the area of our country - is just beginning. It's worth looking out for them in the night sky, so we're about to check out what these clouds are, at what altitude they occur and when is the best time to observe them.

Noctilucent clouds - definition. What is this sky phenomenon?

Let's start with an explanation of what nlc clouds are. They are mesospheric clouds that form very high in the atmosphere - in an area called the mesosphere, which is practically at the border with space (hence the name mesospheric clouds). The mesosphere is located at an altitude of 50-90 kilometers - depending on the season, while mesospheric clouds are formed at an altitude of about 85-90 kilometers. This makes noctilucent clouds the highest clouds we can see from the Earth's surface. They consist of microscopic ice crystals, and were first observed in 1885 - after the eruption of the Krakatau volcano.

noctilucent clouds over the city

At first, it was believed that silver clouds are formed by volcanic eruptions, but this theory has not been confirmed. To this day, we are not 100% sure what the genesis of their formation is, but the most plausible hypothesis is that they are created due to, for example, meteor flights or even space shuttles, which result in the icing of space dust.

How to identify noctilucent clouds (NLC)?

We can very easily identify night shining clouds in the sky, and no advanced astronomical knowledge is necessary for this. They are arranged in the sky in the form of irregular, lighted, silvery-blue streaks - such an effect is possible due to the fact that noctilucent clouds are illuminated by the sun's rays. Noctilucent clouds may remind us of Cirri, which are also high clouds, but which are located in much lower layers of the atmosphere - in the upper troposphere. However, at night they are black, and dark orange when polluted by city lights. So they are very different in appearance from Noctilucent clouds, which are also much slower moving. NLC clouds should also not be confused with red and pink illuminated clouds, during sunset. This is a completely different, though equally beautiful, phenomenon.

noctilucent clouds over the field

Why are noctilucent clouds so special?

Noctilucent clouds are highly regarded by observers who are passionate about various astronomical or atmospheric phenomena. First of all, their appearance is very original, it is definitely different from that of other clouds. Noctilucent clouds are also easy to photograph, so they are a very good introduction to the adventure of astronomy and astrophotography. And let's not forget that they are the highest clouds we can observe on Earth - this fact in itself is very impressive. Of course, certain conditions must be met for it to be possible to observe them. The position of the Sun is very important, so we can see noctilucent clouds only at a certain time of night and during a specific period of the year.

Noctilucent clouds UK - when can we observe them?

The season for noctilucent clouds begins at the end of May and ends in early August. They appear in the sky quite a long time after sunset - between 11 PM and 1/2 AM, or just before sunrise. The sun must be a few or a dozen degrees below the horizon for its rays to illuminate the noctilucent clouds - only then can they shine in the sky - despite the middle of the night. There also happened such exceptional nights, during which we could admire silver clouds in the sky for practically the whole night.

windmill on background of noctilucent clouds

So we are not able to fully predict when the noctilucent clouds will appear and how long they will be visible. They are not preceded by any atmospheric phenomena, but they can be detected by professional radars, like the one at the Kühlungsborn Research Institute. It scans the mesosphere in real-time, and the chances of noctilucent clouds appearing in the sky on a given night can be assessed on this basis. The charts are available on the institute's website, so we can look at them at any time.

Best ways to watch NLC

As with any observation of the night sky, several conditions must be met for noctilucent clouds to be visible to us. First of all, the sky must be clear of clouds. This can be confusing for us, because, after all, noctilucent clouds are also clouds. So what does this mean in this case? The sky must not contain clouds formed in the lower layers of the Earth's atmosphere. They will eclipse the noctilucent clouds and the views will certainly not be as spectacular as they could be with clear skies.

Another important point is the location of the observation spot. It is best if it is on the outskirts of the city, where the sky is not obscured by buildings or tall trees. Luminous noctulous clouds will also certainly be more visible in an area that is not polluted by artificial light. Once we find such a place, all we need to admire the clouds is our own eyes or a small telescope to get a better look at them.

 

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