NCAS CAO NLC-Camera Time-Lapse Video starting at 2020-06-21 20:00 UTC

Abstract

A time-lapse video showing Noctilucent Clouds (NLCs) seen from southern England (51.15°N,-1.44°E) during the night of 21st/22nd June 2020. NLCs are a seasonal wonder of the natural world. They can only be seen from upper-middle and high latitudes during the mid-summer months (between mid May and mid August in the northern hemisphere). They are the result of ice crystals forming at the extraordinarily high altitude of around 82 km. This is 70 km higher than virtually all other clouds seen at these latitudes and qualifies as being at the edge of space (the atmospheric density and pressure are approximately 100,000th of their values at sea level). NLCs can only be seen during twilight hours, hence the name noctilucent, which means night-shining. In this video there is a mild display of NLCs during the dusk followed by a much more impressive display during the dawn. Note that British Summer Time (BST) is one hour ahead of Coordinated Universal Time (UTC). The solar elevation angles do not take account of atmospheric refraction, which is only noticeable when the sun is close to the horizon