Validation of CIE sky models using luminance data from Gurgaon and Chennai, India

The accurate modelling of sky luminance is essential for various applications in architectural design, daylighting analysis, and climate studies. This research paper investigates the effectiveness of the CIE (International Commission on Illumination) sky models by validating them against luminance data collected from two distinct urban environments in India: Gurgaon and Chennai. The study aims to assess how well the CIE models represent the sky conditions in these geographically and climatically diverse cities.

Luminance data were captured using calibrated sky scanner since 2022 in both Gurgaon and Chennai. The collected data were analyzed to characterize the local sky luminance distributions and to identify any significant deviations from the standard CIE sky models. This analysis involved a comprehensive comparison of observed luminance values derived through the CIE models, focusing on key parameters such as the luminance distribution and the sky’s angular dependency.

The results reveal notable differences in sky luminance patterns between the two cities, attributed to their distinct climatic conditions—Gurgaon’s semi-arid climate versus Chennai’s tropical climate. The validation process demonstrated that while the CIE sky models provide a general approximation of sky luminance, they exhibit varying degrees of accuracy when applied to different urban environments. In Gurgaon, the CIE models showed reasonable agreement with observed data, whereas in Chennai, discrepancies were observed due to higher humidity and atmospheric conditions affecting sky luminance.