Noctilucent Clouds in Alaska during 1962

Zones of the visibility of a noctilucent cloud

“…Within the interval of 82 3 km there is half of all the NLC heights measured. The extreme height limits range from 74 km to 92 km (Fogle, 1966). Any change of height can only result in rather insignificant deviations from our results.…”

Noctilucent clouds

“…However, lack of observations from some parts of the world can easily lead to premature conclusions. Until recently it was considered that the lack of observations from Arctic America was significant, but systematic observations now started at College, Alaska (Fogle, 1962) show that the clouds may be as frequent in occurrence there as in Scandinavia and Siberia-from where all our observations have come until recently. The latitudes from which the clouds are most frequently seen are characterized by poor visibility conditions during the critical weeks of summer, and experience in Sweden has shown how useful high-flying aircraft would be as an observational aid.…”

correspondence

“…A possible factor may have been a coincidental auroral display, the extent of which rivaled that of the noctilucent clouds. It has been suggested by Fogle (1966) that heating of the upper mesosphere by aurorae can raise the temperature of the NLC environment so as to degenerate existing NLC displays, or shorten or even preclude them, presumably by inducing sublimation of ices to a point where the clouds The dearth of sightings spanning both twilight intervals is unusual, for most NLC displays of such great extent tend to remain fixed over large areas long enough to permit observation in both evening and morning twilight. The mathematical representation of hydrological processes has a long history, but it is only within the last two decades that hydrological models have become sufficiently comprehensive and widely available as operational tools.…”