Enhancement events of solar radiation

Can be the solar radiation at surface recorded under cloudy conditions higher than its equivalent cloud-free value?. The answer is affirmative and the reason is a curious effect called enhancement which is related to broken clouds conditions. Even the extreme cases can origin values of solar radiation at surface higher than the corresponding values at the top of the atmosphere.

My colleague Ana A. Piedehierro has just published a really interesting paper in Atmospheric Research journal about this subject. This article shows a detailed analysis of the enhancement episodes recorded in Granada (Spain) during five years.  For all detected episodes (about 6% of all experimental data), the relative increases over the expected cloud-free values reached values up to 50%. The duration of the analyzed enhancement events exceeded one hour in some occasions which highlight the great interest of these episodes.

Please find the article at:

Piedehierro_Atmos_Res_2013