Comparison between winter and summer sky-luminance distribution in Central Europe and in the Eastern Mediterranean
Comparison between winter and summer sky-luminance distribution in Central Europe and in the Eastern Mediterranean
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DOI：
10.1016/j.jastp.2004.12.008
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发表时间：
2005-05
影响因子：
1.9
通讯作者：
A. Bartzokas;H. Kambezidis;S. Darula;R. Kittler
中科院分区：
文献类型：
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作者：
A. Bartzokas;H. Kambezidis;S. Darula;R. Kittler
这项工作研究在中欧（布拉迪斯拉发）和另一个在东地中海（雅典）的城市的照度水平，并定义了冬季和夏季的普遍天空亮度分布。所用的数据是5分钟的全球和漫射水平辐照度和照明度沿着与天顶亮度从IDMP站在两个城市为期5年。这项研究是基于CIE最近采用的一套新的天空类型。这些天空标准对应于天顶亮度与漫射水平照度之比对太阳高度的15个理论图。理论曲线在太阳高度35度以上收敛，在许多情况下它们彼此相交。因此，只有当天顶亮度与漫射水平照度之比的值位于描述特定类别的理论曲线周围±2.5%的区域时，每个观测才被归类为15个天空标准之一。如果任何观测被分为多个天空标准，则将全球水平照度与地外水平照度的相应比率与相同太阳高度的所涉及的天空类型的平均比率进行比较，并将观测分类为具有最接近值的天空类型。结果发现，最常见的天空类型布拉迪斯拉发是阴天与陡峭的亮度渐变和轻微的增亮对太阳（冬季）和白蓝色的天空与一个明显的太阳日冕（夏季），而雅典的无云污染的天空盛行在两个季节。研究还发现，在夏季白天，一个明显的转变出现在天空亮度分布在这两个网站。
This work studies the illuminance levels at a city in Central Europe (Bratislava) and another in the Eastern Mediterranean (Athens) and defines the prevailing sky-luminance distributions for winter and summer. The data used are 5-min values of global and diffuse horizontal irradiance and illuminance along with zenith luminance from the IDMP stations at the two cities for a period of 5 years. The study is based on the new set of the sky types recently adopted by CIE. These sky standards correspond to 15 theoretical diagrams of the ratio of zenith luminance to diffuse horizontal illuminance against solar altitude. The theoretical curves converge above 35∘of solar elevation and in many cases they intersect each other. For this reason, each observation is classified into one of the 15 sky standards, only when the value of the ratio of zenith luminance to diffuse horizontal illuminance lies in a zone of ±2.5% around the theoretical curve describing the specific category. If any observation is classified into more than one sky standards, the corresponding ratio of global horizontal illuminance to extraterrestrial horizontal illuminance is compared to the average ratio of the sky types implicated, for the same solar altitude, and the observation is classified in the sky type with the nearest value. It is found that the most frequent sky types for Bratislava are the overcast sky with steep luminance gradation and slight brightening towards the sun (winter) and the white–blue sky with a distinct solar corona (summer), while for Athens the cloudless polluted sky prevails in both seasons. It is also found that during a summer day, a noticeable shift appears in the sky-luminance distribution at both sites.