Abstract
Maximizing natural illuminance, seeking sustainable ecological development, and saving electricity are very important. The annual total natural light illuminance values of 14 typical Chinese cities in different climate regions were obtained in this study based on solar irradiance data of the cities in the past 50 years (from 1961 to 2010). A luminous efficacy model was integrated in the analysis of data. This study analyzes the overall and inter-annual change trends of total natural light illuminance values in each city. Mann-Kendall test method or nonparametric test method can reveal the changing trend of time series; the method does not require samples to follow a specific distribution and cannot be affected by a few abnormal values. The method is suitable for data with abnormal distribution. In this paper we analyze the trend of natural illuminance levels in 14 Chinese cities by Mann-Kendall trend analysis and Mann-Kendall mutation test. The results show that the overall change trends in the annual total natural light illuminance values in Beijing, Guangzhou, Urumchi, Xian, Xining, Shanghai, Changsha, and Chongqing are extremely obvious; the change trend in Erenhot and Kunming are obvious; and those in Changchun, Yushu, Heihe, and Fuzhou exhibit no change. The inter-annual change trends in the total city illuminance values in Chongqing and Urumchi decreased gradually year by year; those in Beijing, Shanghai, Changsha, Guangzhou, Erenhot, Xian, Xining, and Heihe increased at first and decreased in the later years. The illuminance values in Changchun and Yushu increased initially, decreased, and then increased again; in Kunming, these values decreased initially, increased, and then decreased again. The annual total illuminance values of natural light in some cities significantly decrease, thus affecting the accuracy of architectural daylighting design. The total change trend of natural light illuminance has an insignificant association with Chinese light-climate regions. Many factors influence natural illuminance: the major factors are cloud cover and aerosols from air pollution; the minor factors are water vapor, atmospheric molecular scattering and absorption, and solar activity.
Highlights
Maximizing natural illuminance, seeking sustainable ecological development, and saving electricity are very important
Acquisition of natural illuminance data several cities in China have accumulated annual light climate observation data, more long-term and large-scale light climate observation data are required to determine the changes in China's daylighting climate
Luminous efficacy model Irradiance data can be obtained from the relevant meteorological observatories; luminous efficacy K is the key factor in obtaining data on outdoor natural illuminance
Summary
Maximizing natural illuminance, seeking sustainable ecological development, and saving electricity are very important. Internationale de l’Eclairage (CIE) to acquire daylighting climate observation data from several cities (including Beijing and Chongqing in China) throughout the world [3] Under this program, measuring stations throughout the world participate in a coordinated effort of daylight availability recording. Stations fall in two categories: the general class, in which illuminances and irradiances are the principal quantities measured, and the research class, in which the stations make continuous recordings of sky luminance distributions, as well as of illuminance, irradiances, and other meteorological quantities [4]. After this event, daylighting climate observation research did not undergo further development
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