Explanation of the Brightness and Color of the Sky, Particularly the Twilight Sky

Hulburt, E. O.

doi:10.1364/josa.43.000113

Cited by 67 publications

(43 citation statements)

References 9 publications

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“…In addition, multiply scattered light can come not only from the lower atmosphere, where many aerosol particles are present, but also from the upper atmosphere, where ozone absorption makes the light bluish (Hulburt 1953). According to our additional tests, the effect of ozone is significant for VEAs > 7° (not shown), suggesting that light causing the twilight glow at such high VEAs passes a long distance through the ozone layer.…”

Section: Simulation Results: Mechanism Of Tropospheric Aerosol Effectsmentioning

confidence: 71%

“…As observed from the ground, the twilight sky at the zenith is strongly influenced by the Chappuis band, an absorption band of ozone with a peak wavelength of about 550 to 600 nm, corresponding to a yellow-toorange color. Solar radiation passes a long distance through the stratosphere during twilight, and absorption at the Chappuis band makes the skylight bluer (Hulburt 1953;Adams et al 1974). Stratospheric aerosols also influence the twilight sky.…”

Section: Introductionmentioning

confidence: 99%

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Physical Explanation of Tropospheric Aerosol Effects on Twilight Sky Color Based on Photographic Observations and Radiative Transfer Simulations

Saito

Iwabuchi

Hayasaka

2013

SOLA

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The relationship between the twilight sky and atmospheric state has been studied for the past 50 years, providing a good understanding of the general picture of the radiative transfer process under twilight conditions. However, tropospheric aerosols may strongly affect the spectral characteristics of the twilight glow near the horizon under clear-sky conditions, and the mechanism of this phenomenon is not well understood because of its high complexity. In this study, we observed the twilight sky using a digital camera and calculated the spectral radiance of the twilight sky using a radiative transfer model (RTM). Photographic observations aided by several ground-based radiometric measurements revealed that tropospheric aerosols significantly influenced the twilight sky color. In particular, the sky near the horizon became darker and bluer with increasing aerosol optical depth (AOD), which was consistent with the RTM simulations. The RTM simulations also showed for the first time that bluish multiply scattered light dominated the twilight sky near the horizon and reddish singly scattered light decreased with increasing tropospheric AOD. These simulation results suggest that photographic observations have the potential to characterize tropospheric aerosols under twilight conditions.(Citation: Saito, M., H. Iwabuchi, and T. Hayasaka, 2013: Physical explanation of tropospheric aerosol effects on twilight sky color based on photographic observations and radiative transfer simulations. SOLA, 9, 15−18,

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Section: Simulation Results: Mechanism Of Tropospheric Aerosol Effectsmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

Physical Explanation of Tropospheric Aerosol Effects on Twilight Sky Color Based on Photographic Observations and Radiative Transfer Simulations

Saito

Iwabuchi

Hayasaka

2013

SOLA

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“…It was previously demonstrated that physiologically relevant blue shifts in irradiance spectrum that occur during twilight are a result of the increasing absorption of long visible wavelengths by ozone as the pathlength of direct sunlight through the atmosphere increases (Johnsen et al, 2006;Hulbert, 1953). Johnsen and colleagues reported one spectrum of a full moon sky with the moon at an altitude of 70deg on land, but did not quantify the impact of lunar phase or elevation on this twilight blue-shift effect or measure how these phenomena are altered underwater relative to on land (Johnsen et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

Twilight spectral dynamics and the coral reef invertebrate spawning response

Sweeney

Boch

Johnsen

et al. 2011

Journal of Experimental Biology

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SUMMARYThere are dramatic and physiologically relevant changes in both skylight color and intensity during evening twilight as the pathlength of direct sunlight through the atmosphere increases, ozone increasingly absorbs long wavelengths and skylight becomes increasingly blue shifted. The moon is above the horizon at sunset during the waxing phase of the lunar cycle, on the horizon at sunset on the night of the full moon and below the horizon during the waning phase. Moonlight is red shifted compared with daylight, so the presence, phase and position of the moon in the sky could modulate the blue shifts during twilight. Therefore, the influence of the moon on twilight color is likely to differ somewhat each night of the lunar cycle, and to vary especially rapidly around the full moon, as the moon transitions from above to below the horizon during twilight. Many important light-mediated biological processes occur during twilight, and this lunar effect may play a role. One particularly intriguing biological event tightly correlated with these twilight processes is the occurrence of mass spawning events on coral reefs. Therefore, we measured downwelling underwater hyperspectral irradiance on a coral reef during twilight for several nights before and after the full moon. We demonstrate that shifts in twilight color and intensity on nights both within and between evenings, immediately before and after the full moon, are correlated with the observed times of synchronized mass spawning, and that these optical phenomena are a biologically plausible cue for the synchronization of these mass spawning events.

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“…However, based on actual measurements of the sky brightness taken near summer and winter solstices, it was concluded the conditions could be slightly relaxed to 70 minutes after sunset and 70 minutes before sunrise, due to obstructed near-horizon sightlines reaching the light sensors. While these sunlight-affected entries, making up 40% of all collected, would be excluded for NSB studies, they could potentially be used in the future for studies of atmospheric optical properties through changes in the sky brightness level during twilight (Patat et al 2006;Rozenberg 1966;Hulburt 1953).…”

Section: Data Selectionmentioning

confidence: 99%

Contributions of artificial lighting sources on light pollution in Hong Kong measured through a night sky brightness monitoring network

Pun

Leung

et al. 2014

Journal of Quantitative Spectroscopy and Radiative Transfer

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Light pollution is a form of environmental degradation in which excessive artificial outdoor lighting, such as street lamps, neon signs, and illuminated signboards, affects the natural environment and the ecosystem. Poorly designed outdoor lighting not only wastes energy, money, and valuable Earth resources, but also robs us of our beautiful night sky. Effects of light pollution on the night sky can be evaluated by the skyglow caused by these artificial lighting sources, through measurements of the night sky brightness (NSB). The Hong Kong Night Sky Brightness Monitoring Network (NSN) was established to monitor in detail the conditions of light pollution in Hong Kong. Monitoring stations were set up throughout the city covering a wide range of urban and rural settings to continuously measure the variations of the NSB. Over 4.6 million night sky measurements were collected from 18 distinct locations between May 2010 and March 2013. This huge dataset, over two thousand times larger than our previous survey (Pun & So 2012), forms the backbone for studies of the temporal and geographical variations of this environmental parameter and its correlation with various natural and artificial factors. The concepts and methodology of the NSN were presented here, together with an analysis of the overall night sky conditions in Hong Kong. The average NSB in Hong Kong, excluding data affected by the Moon, was 16.8 mag arcsec −2 , or 82 times brighter than the dark site standard established by the International Astronomical Union (IAU) (Smith 1979). The urban night sky was on average 15 times brighter than that in a rural location, firmly establishing the effects of artificial lighting sources on the night sky.

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Explanation of the Brightness and Color of the Sky, Particularly the Twilight Sky

Cited by 67 publications

References 9 publications

Physical Explanation of Tropospheric Aerosol Effects on Twilight Sky Color Based on Photographic Observations and Radiative Transfer Simulations

Physical Explanation of Tropospheric Aerosol Effects on Twilight Sky Color Based on Photographic Observations and Radiative Transfer Simulations

Twilight spectral dynamics and the coral reef invertebrate spawning response

Contributions of artificial lighting sources on light pollution in Hong Kong measured through a night sky brightness monitoring network

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