Geographic Dependence of the Solar Irradiance Spectrum at Intermediate to High Frequencies

Golan Bel,M M Bandi

doi:10.1103/physrevapplied.12.024032

Abstract

Temporal fluctuations in solar irradiance are important in energy harvesting and the study of ecological systems and climate. As solar irradiance is not stationary, analysis is often made in the frequency domain, rather than the time domain, and the power-law spectrum is often attributed to atmospheric effects, such as dust and clouds. The authors show that the power-law spectrum of solar irradiance appears even for a clear sky, due to modulation of the diurnal oscillations caused by varying daylight duration. Thus the power law depends on geographical location, and one must account for the multiplicative effect of atmospheric factors on the clear-sky power-law spectrum.

Highlights

The solar irradiance is directly or indirectly responsible for almost all life and energy processes on the Earth
Having established the spectral power law and the observable difference in it between the measured and calculated spectra, we employ only calculated (CSM and CSMTL1) spectra in our analysis. This allows us to disentangle signal variability from local topography, cloud passage, etc. and focus exclusively on the geographic dependence
We show that a power-law dependence appears in both measured and calculated solar radiation and is not limited to the previously reported power-law dependence of the spectra of solar power generation

Summary

Introduction

The solar irradiance is directly or indirectly responsible for almost all life and energy processes on the Earth. It plays an important role in the analysis and modeling of climate [1,2] and of ecological systems [3,4,5]. Only slow variations in the solar irradiance are deemed important for climatic and ecological processes, and fluctuations on subdaily timescales are averaged out, cases to the contrary do exist [6,7,8,9]. The importance of understanding the geographic dependence of the spectral characteristics of the solar irradiance cannot be overemphasized

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Discussion

Conclusion