Abstract
This paper focuses on different ways of characterizing the solar radiative regime of a day and the stability of this regime. The days may be stratified in classes of cloud shade, observed total cloud cover amount, daily averaged clearness index, and fractal dimension of the solar global irradiance signal. A new Boolean parameter related to solar irradiance fluctuation is defined, namely the sunshine stability number. The time averaged value of the sunshine stability number is used for the characterization of the radiative regime stability during a given time interval. Ranking the days from the view-point of the stability of their radiative regime is performed by using the daily average value of the sunshine stability number and appropriately defined values of disorder and complexity, respectively. Measurements performed in the Romanian town of Timisoara (latitude 45°46′ N, longitude 21°25′ E and 85 m altitude above mean sea level) are used here. They refer to time series of global and diffuse solar irradiance recorded at 15-s time interval between sunrise and sunset during all the days in 2009.
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Abbreviations
- C :
-
Total cloud cover amount
- D :
-
Fractal dimension
- k t :
-
Clearness index
- ξ :
-
Sunshine number
- ζ:
-
Sunshine stability number
- κ:
-
Cloud shade
- σ:
-
Relative sunshine
- Δτ :
-
Sampling time interval (s)
- Δ x :
-
Disorder associated to a random Boolean variable x
- Ω x :
-
Order associated to a random Boolean variable x
- \( \Gamma_x^{ab} \) :
-
Complexity of disorder strength a and order strength b associated to a random Boolean variable x
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Acknowledgments
The authors thank Dr. Samia Harrouni (USTHB University, Algiers) and an anonymous referee for useful comments and suggestions. Financial support from the Romanian Ministry of Research and Education (contract PN II no. 21039/2007) for building Solar Radiation Monitoring Station of the West University of Timisoara is gratefully acknowledged by MP.
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1 Diurnal variation of the sunshine number ξ in all the days with mean cloud shade 0.1–0.2. 2 Diurnal variation of the sunshine number ξ in all the days with mean cloud shade 0.8–0.9. 3 Diurnal variation of the sunshine stability number ζ in all the days with mean cloud shade 0.1–0.2. 4 Diurnal variation of the sunshine stability number ζ in all the days with mean cloud shade 0.8–0.9 (PDF 252 kb)
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Paulescu, M., Badescu, V. New approach to measure the stability of the solar radiative regime. Theor Appl Climatol 103, 459–470 (2011). https://doi.org/10.1007/s00704-010-0312-9
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DOI: https://doi.org/10.1007/s00704-010-0312-9