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

A mathematical method for accurately determining the upper and lower diffuse-fraction (k<sub>d</sub>) 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<s...

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Main Authors:	Harry D. Kambezidis, Styliani I. Kampezidou, Dimitra Kampezidou
Format:	Article
Language:	English
Published:	MDPI AG 2021-09-01
Series:	Applied Sciences
Subjects:	mathematical determination diffuse fraction sunshine duration
Online Access:	https://www.mdpi.com/2076-3417/11/18/8654

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spelling	doaj-c36b368702a245d592b5af9c51e3b6f62021-09-25T23:41:50ZengMDPI AGApplied Sciences2076-34172021-09-01118654865410.3390/app11188654Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any SiteHarry D. Kambezidis0Styliani I. Kampezidou1Dimitra Kampezidou2Atmospheric Research Team, Institute of Environmental Research and Sustainable Development, National Observatory of Athens, GR-11810 Athens, GreeceAerospace Systems Design Laboratory, Georgia Institute of Technology, 275 Ferst Dr NW, Atlanta, GA 30313, USADepartment of Ecology and Environmental Science, University of Umeå, S-90187 Umeå, SwedenA mathematical method for accurately determining the upper and lower diffuse-fraction (k<sub>d</sub>) 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<sub>d</sub> values for these sites are determined from scatter plots of direct-normal solar radiation vs. k<sub>d</sub> 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<sub>d</sub> limits. Plots of sunshine duration (SSD) vs. k<sub>d</sub> are prepared for 12 of the 14 sites. These plots show a decreasing trend in SSD with increasing values of k<sub>d</sub>, as anticipated. According to local climatology, the number of the SSD values in each sky-condition classification varies from site-to-site.https://www.mdpi.com/2076-3417/11/18/8654mathematical determinationdiffuse fractionsunshine duration
collection	DOAJ
language	English
format	Article
sources	DOAJ
author	Harry D. Kambezidis Styliani I. Kampezidou Dimitra Kampezidou
spellingShingle	Harry D. Kambezidis Styliani I. Kampezidou Dimitra Kampezidou Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any Site Applied Sciences mathematical determination diffuse fraction sunshine duration
author_facet	Harry D. Kambezidis Styliani I. Kampezidou Dimitra Kampezidou
author_sort	Harry D. Kambezidis
title	Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any Site
title_short	Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any Site
title_full	Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any Site
title_fullStr	Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any Site
title_full_unstemmed	Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any Site
title_sort	mathematical determination of the upper and lower limits of the diffuse fraction at any site
publisher	MDPI AG
series	Applied Sciences
issn	2076-3417
publishDate	2021-09-01
description	A mathematical method for accurately determining the upper and lower diffuse-fraction (k<sub>d</sub>) 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<sub>d</sub> values for these sites are determined from scatter plots of direct-normal solar radiation vs. k<sub>d</sub> 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<sub>d</sub> limits. Plots of sunshine duration (SSD) vs. k<sub>d</sub> are prepared for 12 of the 14 sites. These plots show a decreasing trend in SSD with increasing values of k<sub>d</sub>, as anticipated. According to local climatology, the number of the SSD values in each sky-condition classification varies from site-to-site.
topic	mathematical determination diffuse fraction sunshine duration
url	https://www.mdpi.com/2076-3417/11/18/8654
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Mathematical Determination of the Upper and Lower Limits of the Diffuse Fraction at Any Site

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