, Volume 282, Issue 2, pp 615-627
Date: 12 Oct 2012

On the Relation Between Solar Activity and Clear-Sky Terrestrial Irradiance

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The Mauna Loa Observatory record of direct-beam solar irradiance measurements for the years 1958 – 2010 is analysed to investigate the variation of clear-sky terrestrial insolation with solar activity over more than four solar cycles. The raw irradiance data exhibit a marked seasonal cycle, extended periods of lower irradiance due to emissions of volcanic aerosols, and a long-term decrease in atmospheric transmission independent of solar activity. After correcting for these effects, it is found that clear-sky terrestrial irradiance typically varies by ≈ 0.2±0.1 % over the course of the solar cycle, a change of the same order of magnitude as the variations of the total solar irradiance above the atmosphere. An investigation of changes in the clear-sky atmospheric transmission fails to find a significant trend with sunspot number. Hence there is no evidence for a yet unknown effect amplifying variations of clear-sky irradiance with solar activity.

An erratum to this article can be found at http://dx.doi.org/10.1007/s11207-013-0232-9.