Noctilucent cloud season 2020 kicks off
BEST TIME TO SEE: All month long at the stated times
It’s noctilucent cloud (NLC) season once again, June and July representing the best possible times to catch sight of these elusive, high altitude ice clouds. NLCs have a direct connection with astronomy. They are a high-altitude phenomenon, occurring at a height of 82km in the mesosphere. NLCs are ice sheets composed of myriad tiny ice crystals. The seeding particles around which these ice crystals form is predominantly meteor dust.
As a meteoroid vaporises in the atmosphere, it leaves tiny dust particles behind. When these encounter supercooled water vapour in the mesosphere, tiny ice crystals form around them, creating the ice sheets that appear as noctilucent clouds.
Being so high, these ice sheets remain bathed in sunlight for a time after the Sun has set for us on the ground. As they reflect sunlight pretty well, they appear illuminated against the deep twilight of a summer night. There is no guarantee that they will appear at all and a bright display one night doesn’t mean there will be a display on the next.
The short June nights are manageable in this respect. Start looking low above the northwest horizon 90-120 minutes after sunset or a similar time low above the northeast horizon before sunrise. A display may appear in the northwest, track through north and end in the northeast.
NLCs appear to shine against a darkened sky – hence the name ‘noctilucent’ which means night shining. They typically have a delicate network-like appearance which remains low in the sky as seen from the UK. However, it has been noted that in recent years the tendrils of NLCs can extend high, especially as dawn approaches. Last year we had several bright, dramatic displays. Only time will tell what 2020 has in store.
For a beginner’s guide to noctilucent clouds turn to page 26