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Dundee is at an almost ideal latitude to observe Noctilucent Clouds (NLC) during the summer months. The name simply means night luminous and these delicate pearly white or bluish clouds may be seen towards the north after the sun has set, and when it is more than six degrees below the horizon.

• They can remain in the northern sky all night and fade in the dawn light.
• The clouds may only be a few degrees above the horizon or sometimes can rise to more than sixty degrees.
• They often form patterns of bands or herringbone waves.
• NLC are the highest clouds on Earth at an altitude of 82km, and form in the extremely cold mesophere from small amounts of water vapour, forming ice round tiny particles which may be meteoric dust.

NLC were first reported in 1885 and seem to have been increasing in frequency ever since. During the past four years – 2006 and 2009 –  there have been displays almost every night in June and July with particularly bright displays in 2009.

Thirty or forty years ago, observers considered themselves fortunate to see four or five displays each year. Some scientists have suggested that NLC may be a barometer of global warming, as more water vapour finds its way into the upper atmosphere.

These clouds are a beautiful and fascinating sight which is easily seen without the need for telescopes or binoculars. Recording their presence may be useful in determining possible changes in climatic conditions.

Anyone interested in learning about NLC, or indeed anyone who would like to report seeing them during 2010 can contact Ken Kennedy – ken.kennedy42@btinternet.com – co-ordinator for NLC observations for the UK and Western Europe.

 

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