engleski

Testing a link between solar irradiance and cloud cover over short timescales

Although over centennial and greater timescales solar variability may be one of the most influential climate forcing agents, the extent to which solar activity may influence climate over shorter time periods is still currently poorly understood. If such a link is operating, it is likely via a mechanism connected to one (or a combination) of the following three parameters: total solar irradiance (TSI), ultraviolet (UV) spectral irradiance, or the galactic cosmic ray (GCR) flux. In this work, we present an analysis based around a superposed epoch (composite) approach focusing on the largest TSI variations obtained from the Active Cavity Radiometer Irradiance Monitor (ACRIM) reconstructions occurring over short (daily) timescales. Using this composite together with the cloud data (ISCCP, MODIS) we test for the presence of a possible link between solar activity and cloud cover over large areas of the globe. The statistical significance of the obtained correlations are evaluated using rigorous statistical techniques such as Monte Carlo simulations. The relevance of our results are also examined in relation to a suggested GCR cloud cover link.

total solar irradiance; TSI; UV; cosmic rays; cloud cover; solar activity; climate

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