The Colour of Noctilucent Clouds

Gadsden, M.

doi:10.1002/j.1477-8696.1975.tb05292.x

Cited by 2 publications

(4 citation statements)

References 8 publications

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“…The finding that absorption in the Chappuis bands of O 3 is not required to explain the blue colour of NLCs in some situations is a new result compared to earlier work (e.g. Gadsden, 1975b).…”

Section: Impact Of the Nlc Optical Depthmentioning

confidence: 46%

“…In good qualitative agreement with our results, the population of small particles leads to positions in the blue part of the chromaticity diagram, whereas the population of large particles leads to yellowish colours. Ostdiek and Thomas (1993) neglect refraction, and Gadsden (1975b) considers it but argues that its effect is very small. Ostdiek and Thomas (1993) a test was carried out that showed that refraction does affect the radiance values but has a minor impact on the spectral shape of the scattering spectra and consequently also on the chromaticity values.…”

Section: Discussionmentioning

confidence: 99%

“…Hulburt's 1953 paper demonstrated that ozone absorption must be taken into account for the correct modelling of colours and spectra of the twilight sky, including the zenith (Hulburt, 1953). Studies on the colours of NLCs are also found in the papers of Gadsden (1975b) and Ostdiek and Thomas (1993). Gadsden analysed spectral radiance and small-field spectral polarisation measurements and highlighted ozone as a decisive factor influencing the colour of NLCs (Gadsden, 1975b).…”

Section: Introductionmentioning

confidence: 99%

“…Studies on the colours of NLCs are also found in the papers of Gadsden (1975b) and Ostdiek and Thomas (1993). Gadsden analysed spectral radiance and small-field spectral polarisation measurements and highlighted ozone as a decisive factor influencing the colour of NLCs (Gadsden, 1975b). In contrast, Ostdiek and Thomas investigated the influence of two different cloud particle size distributions on the colour (chromaticity values) of NLCs (Ostdiek and Thomas, 1993).…”

Section: Introductionmentioning

confidence: 99%

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On the colour of noctilucent clouds

et al. 2022

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Abstract. The high-latitude phenomenon of noctilucent clouds (NLCs) is characterised by a silvery-blue or pale blue colour. In this study, we employ the radiative transfer model SCIATRAN to simulate spectra of solar radiation scattered by NLCs for a ground-based observer and assuming spherical NLC particles. To determine the resulting colours of NLCs in an objective way, the CIE (International Commission on Illumination) colour-matching functions and chromaticity values are used. Different processes and parameters potentially affecting the colour of NLCs are investigated, i.e. the size of the NLC particles, the abundance of middle atmospheric O3 and the importance of multiply scattered solar radiation. We affirm previous research indicating that solar radiation absorption in the O3 Chappuis bands can have a significant effect on the colour of the NLCs. A new result of this study is that for sufficiently large NLC optical depths and for specific viewing geometries, O3 plays only a minor role for the blueish colour of NLCs. The simulations also show that the size of the NLC particles affects the colour of the clouds. Cloud particles of unrealistically large sizes can lead to a reddish colour. Furthermore, the simulations show that the contribution of multiple scattering to the total scattering is only of minor importance, providing additional justification for the earlier studies on this topic, which were all based on the single-scattering approximation.

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Section: Impact Of the Nlc Optical Depthmentioning

confidence: 46%