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Applied Optics

Applied Optics


  • Vol. 42, Iss. 3 — Jan. 20, 2003
  • pp: 445–457

Measuring and Modeling Twilight’s Purple Light

Raymond L. Lee and Javier Hernández-Andrés  »View Author Affiliations

Applied Optics, Vol. 42, Issue 3, pp. 445-457 (2003)

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During many clear twilights, much of the solar sky is dominated by pastel purples. This purple light’s red component has long been ascribed to transmission through and scattering by stratospheric dust and other aerosols. Clearly the vivid purples of post-volcanic twilights are related to increased stratospheric aerosol loading. Yet our time-series measurements of purple-light spectra, combined with radiative transfer modeling and satellite soundings, indicate that background stratospheric aerosols by themselves do not redden sunlight enough to cause the purple light’s reds. Furthermore, scattering and extinction in both the troposphere and the stratosphere are needed to explain most purple lights.

© 2003 Optical Society of America

OCIS Codes
(010.1290) Atmospheric and oceanic optics : Atmospheric optics
(330.1710) Vision, color, and visual optics : Color, measurement
(330.1730) Vision, color, and visual optics : Colorimetry

Raymond L. Lee and Javier Hernández-Andrés, "Measuring and Modeling Twilight’s Purple Light," Appl. Opt. 42, 445-457 (2003)

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  28. The × to the right of Fig. 11’s 5–3-00 purity maximum occurred on 6–11–01. Although this × is more purplish than the 5–3-00 maximum, the 6–11–01 maximum is actually closer to the chromaticity of 5–2-00. Thus the largest chromaticity shift that we measured is from 5–2-00 to 5–3-00, even though Fig. 11’s anisotropic scaling suggests otherwise.
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