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Abstract: This paper presents a universal model of luminous efficacy for direct solar radiation on a horizontal surface. The model is applicable to all sky conditions and is based on data obtained from satellites and available via web servers. Solar radiation data from 10 locations in Europe and North Africa has been used to obtain four functions for luminous efficacy (K) against the sole independent variable solar altitude (α). Additionally cloud amount (C) was been used to obtain four other functions. All were used to accurately estimate illuminance for the 10 originating locations; for four locations based on satellite data; and for a further four based on measured data. A statistical assessment showed that three models performed best, namely, K against 1/α, K against sin α, and K against C/α. Comparison between results from the proposed models, and those produced using three previously published models, indicate that the former produce more accurate estimates of luminous efficacy. The satellite based approach makes daylight data available in locations remote from current measurement sites. [ABSTRACT FROM AUTHOR]

Abstract: Thermochronological studies of Variscan basement in Iberia yield cooling ages typically younger than ~200 Ma. In this paper, we explore the regional implications of this recurrent age maximum by examination of low and high temperature thermochronological datasets from all over Iberia. Based on these results, we show that in general the lack of cooling ages older than 200 Ma is the result of several important regional periods of thermal resetting. Resetting took place in areas of extension and burial during the Mesozoic break-up of Pangea. Evidence for large scale magmatism and mineralisation is found in Iberia during the Mesozoic, since at that time Iberia formed part of the Central Atlantic Magmatic Province and a large mineralization province extending from North Africa to Western Europe. Numerical modelling allows us to assess the conditions under which rocks in the upper crust may have been thermally reset and the mechanisms likely involved. Results show that active rifting combined with shallow magmatism, and to a lesser extent deep sedimentary burial, could have led to an increase of the geothermal gradient up to ~73 °C/km and the reset of thermochronometers with closure temperatures up to 200 °C. Yet, we suggest that also hydrothermal activity, associated to extensional basins, played an important role to the increase of temperatures of some basement rocks above 300 °C. [Copyright &y& Elsevier]