Upgrade of SMHI's meteorological radiation network 2006-2007 - Effects on direct and global solar radiation

Typ: Rapport
Serie: Meteorology 148
Författare: Thomas Carlund


The radiation network of SMHI was modernized in 2006-2007. Old measurements were closed down after 6-18 months of parallel operation of new and old measurements. This study reports the results of the comparison mainly between the old and new global and direct solar radiation measurements. On average the agreement between old and new measurements was good. The network average of ratios of whole period values was for global radiation 0.997 and for direct radiation 1.009. None of these results are significantly different from one at a level of confidence of 90 %. Despite the fairly good agreement some systematic differences between the old and new measurements were found. The differences are mainly thought to be caused by a difference in the apparent directional response between the old and new pyranometers and different viewing geometries in the old and new pyrheliometers. Functions to correct old global and direct radiation have been developed. These should be used to increase the homogeneity in Swedish solar radiation data from 1983and onwards, especially for monthly data. A new measurement method and new instruments for determination of sunshine duration were introduced in the upgraded network. A more detailed study comparing sunshine duration measurements by pyrheliometers in the old network and by contrast sensors in the modernized network, probably based on 1-minute or even instantaneous data, needs to be done in the future.