Noctilucent Clouds

Gadsden, M.; Schröder, Wilfried

doi:10.1007/978-3-642-48626-5_1

Cited by 144 publications

(208 citation statements)

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“…Particles can take hours to grow to visible sizes, but evaporation times approach seconds when temperatures are raised (Gadsden and Schröder, 1989). Thus, while the long-term effect of short-period waves on NLC will be to reduce their visibility (Rapp et al, 2002), the bright and dark periodic structures in the NLC, with time scales of minutes, are primarily due to the density perturbations caused by the gravity wave rather than changes in the particle radius due to temperature effects (Jensen and Thomas, 1994).…”

Section: Extracting the Amplitudesmentioning

confidence: 99%

Characteristics and sources of gravity waves observed in noctilucent cloud over Norway

et al. 2014

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Abstract. Four years of noctilucent cloud (NLC) images from an automated digital camera in Trondheim and results from a ray-tracing model are used to extend the climatology of gravity waves to higher latitudes and to identify their sources during summertime. The climatology of the summertime gravity waves detected in NLC between 64 and 74 • N is similar to that observed between 60 and 64 • N by Pautet et al. (2011). The direction of propagation of gravity waves observed in the NLC north of 64 • N is a continuation of the north and northeast propagation as observed in south of 64 • N. However, a unique population of fast, short wavelength waves propagating towards the SW is observed in the NLC, which is consistent with transverse instabilities generated in situ by breaking gravity waves . The relative amplitude of the waves observed in the NLC Mie scatter have been combined with raytracing results to show that waves propagating from near the tropopause, rather than those resulting from secondary generation in the stratosphere or mesosphere, are more likely to be the sources of the prominent wave structures observed in the NLC. The coastal region of Norway along the latitude of 70 • N is identified as the primary source region of the waves generated near the tropopause.

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Section: Extracting the Amplitudesmentioning

confidence: 99%

Characteristics and sources of gravity waves observed in noctilucent cloud over Norway

et al. 2014

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“…These are expertly summarized by Fogle and Haurwitz (1966) and by Gadsden and Schröder (1989). No attempt is made to make a complete review of NLC science in this short report, only the most important characteristics are mentioned, which are of relevance for the present study, which concerns possible trends over the last 43 years.…”

Section: Introductionmentioning

confidence: 99%

Noctilucent clouds observed from the UK and Denmark – trends and variations over 43 years

2008

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Abstract. The combined UK/Denmark record of noctilucent cloud (NLC) observations over the period is analysed. This data set is based on visual observations by professional and voluntary observers, with around 40 observers each year contributing reports. Evidence is found for a significantly longer NLC season, a greater frequency of bright NLC, and a decreased sensitivity to 5-day planetary waves, from 1973-1982, compared to the rest of the time interval. This coincides with a period when the length of the summer season in the stratosphere was also longer (defined by zonal winds at 60 • N, 30 hPa). At NLC heights, lower mean temperatures, and/or higher water vapour and/or smaller planetary wave amplitudes could explain these results. The time series of number of NLC nights each year shows a quasi-decadal variation with good anti-correlation with the 10.7 cm solar flux, with a lag of 13-17 months. Using multi-parameter linear fitting, it is found that the solarcycle and the length of summer in the stratosphere together can explain ∼40% of the year-to-year variation in NLC numbers. However, no statistically confidant long-term trend in moderate or bright NLC is found. For NLC displays of moderate or greater intensity, the multi-parameter fit gives a trend of ∼0.08 nights (0.35%) per year with a statistical probability of 28% that it is zero, or as high as 0.16 nights (0.7%) per year. There is a significant increasing trend in the number of reports of faint or very faint NLC which is inconsistent with other observations and may be due changes in observing practices.

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“…The visible structure of NLCs is similar to cirrus clouds, but the former show more intensive and complex structures with signatures of turbulent vortices and waves of different scales. Noctilucent clouds are composed of water ice crystals of 30-100 nm in radius that scatter a sufficient amount of sunlight and thus NLCs are readily seen against the dark twilight sky from May until September (Gadsden and Schröder, 1989).…”

Section: Introductionmentioning

confidence: 99%

“…The history of the first observations of NLCs is well described in the canonical books by Bronsten and Grishin (1970) and by Gadsden and Schröder (1989), and we refer the interested reader to these sources (and therein references). The purpose of the present paper is to address specific issues that have been missed in the literature on noctilucent clouds: (1) atmospheric impact of the major volcanic eruptions during the period of 1783-1883; (2) the year of the earliest known observations; (3) the earliest photographic registrations and height estimations of noctilucent clouds.…”

Section: Introductionmentioning

confidence: 99%

Notes on historical aspects on the earliest known observations of noctilucent clouds

Dalin

Pertsev

Romejko

2012

Hist. Geo Space. Sci.

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Abstract. The present paper considers historical aspects of the earliest known observations of noctilucent clouds (NLCs). The 1884 and 1885 are discussed by considering important historical citations by the pioneers of the earliest known observations of noctilucent clouds. For the first time in NLC studies, we consider seven major volcanic eruptions: Laki in 1783, Mount St. Helens in 1800, Tambora in 1815, Galunggung in 1822, Cosigüina in 1835, Shiveluch in 1854 and Askja in 1875. These all preceded the catastrophic 1883 eruption of Krakatoa, which despite having a lesser magnitude than Tambora in 1815, had pronounced effects on the atmosphere. These eruptions represent possible triggers for the appearance of NLCs. For the first time, we publish an unknown, in English-speaking literature, historical fact on the first determinations of the altitude of noctilucent clouds made by two Russian astronomers V. K. Tseraskii and A. A. Belopolskii on 26 June 1885, who managed to infer the altitude of the clouds in the range of 73–83 km, that is, for the first time, demonstrating the possible existence of the clouds at great altitudes in the Earth's atmosphere. Moreover, V. K. Tseraskii was the first observer to photograph noctilucent clouds in 1885 or 1886, which is 1–2 yr before the German astronomer O. Jesse, who owns the first published images of noctilucent clouds. The photographs made by V. K. Tseraskii, unfortunately, did not reach us.

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Noctilucent Clouds

Cited by 144 publications

References 0 publications

Characteristics and sources of gravity waves observed in noctilucent cloud over Norway

Characteristics and sources of gravity waves observed in noctilucent cloud over Norway

Noctilucent clouds observed from the UK and Denmark – trends and variations over 43 years

Notes on historical aspects on the earliest known observations of noctilucent clouds

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