A note of double-layer cloud detection method based on cloud base height and brightness

• Published in: Solar energy 2024-09, Vol.279, p.112845, Article 112845
• Main Authors: Niu, Yisen, Lin, Xilong, Zou, Lianglin, Song, Jifeng, Yan, Zixuan, Tang, Ping, Wang, Qian, Wang, Bingnan
• Format: Article
• Language: English
• Subjects: Cloud base height; Cloud detection; Double-layer clouds; Ground-based cloud image
• ISSN: 0038-092X
• DOI: 10.1016/j.solener.2024.112845

•Double-layer cloud detection method for visible cloud image is proposed.•Double-layered clouds usually have different brightness, serving as the basis for detecting their shape.•The cloud base height serves as the basis for double-layered cloud judgment.•This method achieves an accuracy of 98.3% and 80.5% under non-overlapping and overlapping double-layer cloud conditions, respectively. Double-layer cloud is a special cloud condition, and clouds in two layers have different effects on solar radiation reaching ground. Getting the shape of double-layer clouds is helpful to study the change of solar irradiance. The proposed double-layer clouds detection method is based on the cloud base height (CBH) and brightness of double-layer clouds. The CBH is calculated based on binocular parallax, which requires two images filmed synchronously by two cameras, and the brightness is offered by the brightness channel in HSV color space. The accuracy of this method is 98.5% for single-layer clouds and 89.4% for double-layer clouds. The reasons for misidentifications are (1) the brightness contrast decreases when the high-layer clouds are thick, (2) the distant low clouds have different brightness in top and bottom.