Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any Site

Applied Sciences

Styliani I. Kampezidou¹  Harry D. Kambezidis²  Dimitra Kampezidou³ 

[1] Aerospace Systems Design Laboratory, Georgia Institute of Technology, 275 Ferst Dr NW, Atlanta, GA 30313, USA;Atmospheric Research Team, Institute of Environmental Research and Sustainable Development, National Observatory of Athens, GR-11810 Athens, Greece;Department of Ecology and Environmental Science, University of Umeå, S-90187 Umeå, Sweden;

关键词: mathematical determination;    diffuse fraction;    sunshine duration;   

DOI  :  10.3390/app11188654

来源: DOAJ

【 摘 要 】

A mathematical method for accurately determining the upper and lower diffuse-fraction (k_d) limits that divide the sky into clear, intermediate, and overcast is developed. Fourteen sites around the world are selected for demonstrating the methodology. The upper and lower k_d values for these sites are determined from scatter plots of direct-normal solar radiation vs. k_d pairs over the typical meteorological year of each site. They vary between 0.73 and 0.80 for the upper and between 0.24 and 0.27 for the lower k_d limits. Plots of sunshine duration (SSD) vs. k_d are prepared for 12 of the 14 sites. These plots show a decreasing trend in SSD with increasing values of k_d, as anticipated. According to local climatology, the number of the SSD values in each sky-condition classification varies from site-to-site.

【 授权许可】

Unknown