© Mark Zalcik
Clover Bar area, Edmonton, Alberta, Canada
Latitude: 53° 34' 40'' N
Longitude: 113° 20' 37'' W
03 July 2005 0000 (Local Time)
Camera direction: towards NW
Image P/S code: S.10U.3.5
Image I.D.: 5582
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Noctilucent cloud: complex structure
Often in displays of noctilucent cloud, several forms may be seen simultaneously. It is not unusual, therefore, for two or more intersecting or overlapping groups to give rise to complex structures (for example, bright knots or net-like structures) or types that do not fit the standard classifications.
This picture, taken during evening twilight just east of the city of the Edmonton in Alberta, Canada, shows one such complex display of noctilucent cloud. The display was the brightest the observer had seen in 35 years of observing noctilucent cloud and clearly rated as 5 on the 5-point brightness scale. In general, it may be classed as type O, but there is the suggestion of a large-scale ring structure (type IVc) that is essentially a large oval of noctilucent cloud visible in the upper left part of the image.
Links in the image description will highlight features on the image. Mouse over the features for more detail.
© Mark ZalcikClover Bar area, Edmonton, Alberta, CanadaLatitude: 53° 34' 40'' NLongitude: 113° 20' 37'' W03 July 2005 0000 (Local Time)Camera direction: towards NWImage P/S code: S.10U.3.5Image I.D.: 5582
Noctilucent cloud: complex structure
Often in displays of noctilucent cloud, several forms may be seen simultaneously. It is not unusual, therefore, for two or more intersecting or overlapping groups to give rise to complex structures such as bright knots or net-like structures, or types that do not fit the standard classifications. This picture, taken just before midnight from the Edmonton area of Alberta, Canada, shows one such complex display of noctilucent cloud. The central part of the display had a peculiar billow-like appearance with a number of lacunosus holes.
Links in the image description will highlight features on the image. Mouse over the features for more detail.
© Mark ZalcikNamao, Alberta, CanadaLatitude: 53° 43' 2'' NLongitude: 113° 29' 39'' W26 June 2014 2343 (Local Time)Camera direction: towards NWImage P/S code: P.10Image I.D.: 5687
Noctilucent cloud
Noctilucent clouds (NLC) are usually only visible to observers in mid to high latitudes (roughly 50°N to 65°N or 50°S to 65°S) and in the twilight or night sky for a few months in summertime, when temperatures in the mesosphere are the coldest. This photograph was taken in late June, during summer in the northern hemisphere, from a location 55.78°N.
Noctilucent clouds are generally observed during the twilight periods when the Sun is between 6° and 16° below the observer's horizon. It is during this period that the background sky is dark enough for the cloud to be seen, yet the high-altitude clouds are still illuminated by sunlight.
Typically what sets noctilucent clouds visually apart from tropospheric clouds is their visibility in the night and their obvious, and sometimes bright, blue-white colour. The low-level tropospheric clouds at 2 and 3 are within the Earth's shadow and they stand out as dark silhouettes against the relatively brighter background sky. In contrast, noctilucent clouds are always brighter than the twilight sky. Near the horizon, they may have a reddish tint. Two main types of NLC are shown here: bands (type II) – these are long streaks – and billows (type III), seen at 7 and 8 – these are closely spaced, roughly parallel streaks.
Links in the image description will highlight features on the image. Mouse over the features for more detail.
© Ewan KaneEast Kilbride, Scotland, United Kingdom of Great Britain and Northern IrelandLatitude: 55° 46' 49'' NLongitude: 4° 8' 48'' W23 June 2015 2247 (Local Time)Camera direction: towards NWImage P/S code: P.10Image I.D.: 5581