scholarly journals Formulas for luminance distribution on the clear sky and total horizontal illuminance from the clear sky

1991 ◽  
Vol 75 (10) ◽  
pp. 582-589 ◽  
Author(s):  
Seishi Sekine
Keyword(s):  
Clear Sky ◽  
Luminance Distribution

The use of horizontal sky illuminance to classify the CIE Standard General Skies

2016 ◽  
Vol 48 (8) ◽  
pp. 1034-1041 ◽  
Author(s):  
KA Alshaibani
Keyword(s):  
Low Latitude ◽  
Simple Task ◽  
Frequency Distributions ◽  
Clear Sky ◽  
Luminance Distribution ◽  
Long Period ◽  
The World ◽  
Sky Type ◽  
Overcast Sky

The CIE Standard General Skies defines the luminance distribution of skies into 15 types, from overcast sky to clear sky. Finding the frequency distributions of such skies is not a simple task, for two reasons. The first is the need for accurate luminance measurements over a long period of time. Such data are not available in many regions around the world. The second is the difficulty in obtaining accurate readings for the zenith luminance in low latitude climates. This paper presents a method in which the horizontal sky illuminance can be used to classify sky type.

scholarly journals Daylighting on the working plane in oriented attic rooms under overcast and clear sky

2014 ◽  
Vol 9 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Kristián Kondáš ◽  
Stanislav Darula
Keyword(s):  
Main Task ◽  
Distribution Modelling ◽  
Clear Sky ◽  
Luminance Distribution ◽  
New Criterion ◽  
Sky Conditions ◽  
Overcast Sky

AbstractThe evaluation of daylight conditions in building interiors is based on the Daylight Factor concept after current Slovak standards. Criteria and requirements determined in these standards consider the worst daylight exterior conditions which are described by CIE overcast sky model. The sky luminance distribution of overcast sky is centrical to the zenith, so independence of window orientation to cardinal points is characteristic in daylighting calculations. The sky luminance distribution modelling is one of the main task of the daylight source research more than 50 years. It is evident that also other types of sky conditions exist in nature. An introduction of a new criterion based on photometric variables, which also consider sunlight influence, is expected. This article represents a study of the influence of the interior orientation on distribution of daylighting in attic spaces under an overcast and clear sky

scholarly journals Determination of luminance distribution under tropical sky conditions

Vestnik MGSU ◽  
2019 ◽  
pp. 1096-1105
Author(s):  
Nguyen Thi Khanh Phuong
Keyword(s):  
Great Influence ◽  
Research Problem ◽  
Natural Illumination ◽  
The Real ◽  
Clear Sky ◽  
Luminance Distribution ◽  
High Solar Radiation ◽  
Sky Conditions ◽  
Sky Type ◽  
Overcast Sky

Introduction. Natural illumination calculations depend on the sky luminance distribution. The most often used diagram of sky luminance in handbooks and guidelines is the luminance distribution in the cloudy sky proposed by Moon and Spencer. This concept actually includes the tropical areas of Vietnam, where the overcast sky and clear sky does not typically occur. To improve the calculation of natural illumination, it is necessary to determine the luminance distribution in the real sky. Materials and methods. In solving the research problem, the real sky types for Hanoi were identified using the 15 international standard sky types with their descriptions by lighting climate, which is provided using the method by R. Kittler. The descriptions are derived from the data on diffuse horizontal illumination Dv, extraterrestrial horizontal illumination Ev and light turbidity coefficient Tv. For a specific sky type, the standard parameters were selected for calculating the luminance distribution of the real sky. Results. The obtained results show that the typical sky type of Hanoi is the partly cloudy sky, no gradation towards zenith, with slight bleaching towards the Sun (type VI). The sky types from October to December are partly cloudy with the obscured Sun (type IX) and partly cloudy with the more luminant circumsolar area (type X). The study shows that the state of cloud coverage has a great influence on the level of diffuse horizontal illumination and luminance distribution under tropical sky conditions. Conclusions. It is revealed that the typical sky type for Hanoi is neither overcast nor clear sky. A typical sky with statistic dominance of cirrus and stratus clouds under effect of high solar radiation of Vietnamese tropical climate gives a high level of diffuse horizontal illuminance. The results show that the difference in luminance distribution between the CIE standard overcast sky and Kittler’s intermediate sky can be resolved at the angles of sky point elevation above horizon γ is higher than 50° with the relative errors below 10 %. In other words, the luminance distribution β of the considered sky type is significant for a system of side natural illumination.

scholarly journals Modeling of Natural Lighting Parameters in the Open Air with Intermeradiandiate Luminance Distribution

2021 ◽  
Author(s):  
Evgeniy Konopatskiy ◽  
Vladimir Yehorchenkov ◽  
Andrey Bezditnyi
Keyword(s):  
Spherical Segment ◽  
Mathematical Apparatus ◽  
Natural Lighting ◽  
Clear Sky ◽  
Luminance Distribution ◽  
Standard Distribution ◽  
Point Set ◽  
European Standards

When simulating outdoor natural lighting, a spherical sky model is used. This is true in a clear sky, but in the presence of clouds, this model does not correspond to reality. This paper presents the substantiation of the sky model in the form of a spherical segment with a standard distribution of the luminance of the semi-clear (intermediate) sky. Moreover, instead of the ratio of illumination, under given cloudiness conditions to illumination with ideal transparency of the atmosphere, which are usually used in European standards, the direct value of cloudiness is used here, taken from the results of long-term observations at meteorological stations. To modeling the parameters of outdoor natural lighting, a more effective and simple mathematical apparatus of point calculus is used, with the help of which a point set of a spherical segment is formed. On the basis of this set, a field of elementary pyramids is created. For each pyramid, using well-known formulas, elementary values of the parameters of natural lighting are determined.

An Analysis of Nonovercast Sky Luminance Models Against Hong Kong Data

2006 ◽  
Vol 129 (4) ◽  
pp. 486-493 ◽  
Author(s):  
Danny H. W. Li ◽  
Chris C. S. Lau
Keyword(s):  
Hong Kong ◽  
Modern Architecture ◽  
Distribution Model ◽  
Position Change ◽  
Clear Sky ◽  
Luminance Distribution ◽  
Artificial Neural Network Ann ◽  
The Tropics ◽  
Sky Conditions ◽  
Solar Position

Daylighting is an important issue in modern architecture that has been characterized by the use of curtain walls in buildings. Nonovercast skies, including clear and partly cloudy days, are essential because they may occur more frequently for places such as in equatorial regions and the tropics. Better understanding of nonovercast sky luminance distribution is vital to estimate the dynamic variation in daylight illuminance as sky condition and solar position change. This paper presents the work on the evaluation of six clear sky and three partly cloudy sky models against three-year (1999–2001) measured Hong Kong sky luminance data. The general features and characteristics for the models were described and assessed. The nonovercast sky conditions were identified using the ratio of zenith luminance (Lz) to diffuse illuminance (Dv) and the ratio of global illuminance (Gv) to the extraterrestrial illuminance (Ev). Subsequent interpretations of the clear skies into high and low turbid types were conducted in conjunction with the cloud cover (CLD) and the luminous turbidity (Tv), and partly cloudy skies were further subdivided into thin and thick cloud modes using sunshine hour (SH) and global irradiance (GSI). A statistical analysis of the models revealed that the Gusev model (i.e., CIE (Internal Commission on Illumination) polluted sky No. 13) and the model by Chen et al. (1999, “Luminance Distribution Model of Intermediate Skies,” Zhaom Ing Gong Chen Xuebao, 10(1), pp. 59–63 (in Chinese)) developed using artificial neural network (ANN) theory with the measured data in Chongqing, China (29.6degN and 106.5degE) showed the best predictions for sky luminance at this location under the clear and partly cloudy sky conditions, respectively.

Assessment of influence of urban aerosol vertical profile on clear-sky diffuse radiance pattern

2021 ◽  
pp. 1-7
Author(s):  
Jaromir Petrzala
Keyword(s):  
Extinction Coefficient ◽  
Vertical Profile ◽  
Transfer Problem ◽  
Radiative Transfer Problem ◽  
Clear Sky ◽  
Luminance Distribution ◽  
Exponential Law ◽  
Sky Radiance ◽  
Volume Extinction Coefficient ◽  
Aerosol Extinction Coefficient

Abstract Aerosol particles spread in the atmosphere play an important role in solar light scattering and thus co-determine the sky radiance/luminance pattern as well as diffuse irradiances/illuminances at the ground. The particular influence is given by their optical properties and by their distribution in the atmosphere. The dependence of the aerosol extinction coefficient on altitude is usually described by the exponential law, which results from averaging of a large amount of aerosol realizations. This is also frequently the case of simulating of the solar diffuse radiance/luminance distribution over the sky, when it is based on solving the radiative transfer problem. However, the aerosol vertical profile can sometimes be significantly different from the exponential one. Mainly in the urban environment, the aerosol is often well-mixed within the atmospheric boundary layer, so its volume extinction coefficient is almost constant there. This work investigates how such different profiles affect the clear sky radiance pattern and consequently also the ground-based horizontal diffuse irradiance. The numerical simulations reveal that the discrepancies are negligible in practice. So it appears that the aerosol vertical distribution does not play any important role in sky radiance calculations and the standard exponential law is general enough to cover also various specific aerosol conditions.

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