Modeling the night-sky radiances and inversion of multi-angle and multi-spectral radiance data

Kocifaj, Miroslav

doi:10.1016/j.jqsrt.2013.12.002

Cited by 10 publications

(3 citation statements)

References 30 publications

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“…The establishment of an international network of sky brightness monitoring sites should be a high priority. In addition to improving understanding of this global environmental change, the data from such a network are crucially needed to test and improve the increasingly sophisticated skyglow models under development 46 47 48 . These models can then be used to interpolate into regions where monitoring is not taking place, which will greatly aid understanding of the diverse social and environmental costs of skyglow.…”

Section: Discussionmentioning

confidence: 99%

Worldwide variations in artificial skyglow

Kyba

Tong

Bennie

et al. 2015

Sci Rep

154

127

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Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope, and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties. Skyglow is observed to vary over four orders of magnitude, a range hundreds of times larger than was the case before artificial light. Nearly all of the study sites were polluted by artificial light. A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. Overcast skies ranged from a third darker to almost 18 times brighter than clear. Clear sky radiances estimated by the World Atlas of Artificial Night Sky Brightness were found to be overestimated by ~25%; our dataset will play an important role in the calibration and ground truthing of future skyglow models. Most of the brightly lit sites darkened as the night progressed, typically by ~5% per hour. The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program.

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Section: Discussionmentioning

confidence: 99%

Worldwide variations in artificial skyglow

Kyba

Tong

Bennie

et al. 2015

Sci Rep

154

127

View full text Add to dashboard Cite

show abstract

“…Small perturbations on the measured data may have quite a large response in the solution, thus a special mathematical treatment should be applied to determine sought function-e.g., a stabilizing functional is usually introduced to enforce the smoothness of the solution found, to penalize large norms, and, to penalize steep gradients of CEF. Retrieval of the CEF by solving an inverse radiative transfer problem is advantageous because (i) it is cheap enough, (ii) it provides information on the bulk emission function, and (iii) it is also applicable to routinely measured data such as radiance or luminance patterns (Kocifaj 2014a(Kocifaj , 2014b. However, the capabilities of inversion techniques are quite constrained regarding accuracy and information content because data are noisy and sometimes incomplete, and also because the problem is ill-posed (Twomey 2002).…”

Section: Minimum Requirements To Be Fulfilled By the Cef To Ensure A ...mentioning

confidence: 99%

Angular Emission Function of a City and Skyglow Modeling: A Critical Perspective

Kocifaj

Lamphar

2016

PASP

Self Cite

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The radiative transfer equation (RTE) is a common approach to solving the transfer of electromagnetic energy in heterogeneous disperse media, such as atmospheric environment. One-dimensional RTE is a linear boundary value problem that is well suited to plane-parallel atmosphere with no diffuse intensity entering the top of the atmosphere. In nighttime regime, the ground-based light sources illuminate the atmosphere at its bottom interface. However, the light-pollution models conventionally use radiant intensity function rather than radiance. This might potentially result in a number of misconceptions. We focused on similarities and fundamental differences between both functions and clarified distinct consequences for the modeling of skyglow from finite-sized and semi-infinite light-emitting flat surfaces. Minimum requirements to be fulfilled by a City Emission Function (CEF) are formulated to ensure a successful solution of standard and inverse problems. It has been shown that the horizon radiance of a flat surface emitting in accordance with Garstang's function (GEF) would exceed any limit, meaning that the GEF is not an appropriate tool to model skyglow from distant sources. We developed two alternative CEFs to remedy this problem through correction of direct upward emissions; the most important strengths of the modified CEFs are detailed in this paper. Numerical experiments on sky luminance under well-posed and ill-posed boundary conditions were made for two extreme uplight fractions (F) and for three discrete distances from the city edge. The errors induced by replacing radiance with radiant intensity function in the RTE are generally low (15%-30%) if F is as large as 0.15, but alteration of the luminance may range over 1-3 orders of magnitude if F approaches zero. In the latter case, the error margin can increase by a factor of 10-100 or even 1000, even if the angular structure of luminance patterns suffers only weak changes. This is why such a shift in luminance magnitudes can be mistakenly interpreted as the effect of inaccurate estimate of lumens per head of the population rather than the effect of cosine distortion due to ill-posed inputs to the RTE. For that reason, a thorough revision (and/or remediation) of theoretical and computational models is suggested.

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“…In general, the number of works devoted to the influence of SPD on the effect of light pollution is significant [11,[23][24][25][26][27][28][29][30][31][32][33]. Within these studies, there are many works in which analysis of the influence of SPD on light pollution effect is extended by consideration of spectral reflectance of the ground or atmosphere properties.…”

Section: Introductionmentioning

confidence: 99%

Influence of a Light Source Installed in a Luminaire of Opal Sphere Type on the Effect of Light Pollution

Tabaka

Rózga

2020

Energies

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The article presents the results of the studies concerning the influence of a light source installed in luminaire of opal sphere type on the light pollution effect of the night sky. It is known from literature reports that the effect of light pollution is influenced by the spectral distribution of light. Although the influence of the spectral distribution has been widely studied from different perspectives, there is still a need to study this phenomenon—for example, from the point of view of the spectral reflection properties of the ground, on which the lanterns are installed. Hence, the above-mentioned aspect was considered in the authors’ investigations. The luminaire considered has been equipped with 20 different light sources, including the latest generation of lamps (light-emitting diodes, LEDs) as well as the conventional ones. With respect to these light sources, the measurements of light distribution and spectral distribution of emitted radiation of the luminaire were performed. Having these measurement data, the simulations were carried out using the DIALux software, and the calculations were made using the specially prepared calculation tool. On the basis of the results obtained in this way this was stated that the type of light source installed in the luminaire has a significant effect on the sky glow. An important factor affecting light pollution is not only the value of the luminous flux emitted upward but also the spectral characteristics of the emitted radiation, the impact of which is most noticeable. The conclusions from the studies indicate the next steps in the analysis of the light pollution effect. These steps will be focused on extended analysis of LEDs as modern and developed light sources.

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Modeling the night-sky radiances and inversion of multi-angle and multi-spectral radiance data

Cited by 10 publications

References 30 publications

Worldwide variations in artificial skyglow

Worldwide variations in artificial skyglow

Angular Emission Function of a City and Skyglow Modeling: A Critical Perspective

Influence of a Light Source Installed in a Luminaire of Opal Sphere Type on the Effect of Light Pollution

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