Brief history of ground observation networks

Solar irradiance and exposure monitoring by the Bureau of Meteorology has undergone several transformations since it begun in the mid-1960s. At that time a 28 station network was established using Eppley Black & White pyranometers, which provided measurements of 30 minute global and diffuse solar exposure. This network was supplemented by a small network taking data in the capital cities using modest quality black-only Middleton EP07 thermopile pyranometers.

Early solar monitoring equipment
Figure Early-site. Global and diffuse pyranometers at one of the Bureau's early solar monitoring sites. An evaporation tank and wind run anemometer are in the background.

The combined network relied on initial calibration of the pyranometers, and subsequent correction of data by the Bureau using modelled climatology based on measurements in South Africa. Instruments were changed when it was clear they had failed, or their sensitivities were undergoing significant shifts when compared to a theoretical climatology.

Trends suspected to be instrumental were modified to reflect the theoretical climatology rather than by recalibrating the instrument observing the trend. Unfortunately, some of the trends are now known to have been environmental not instrumental. As a result, there is evidence to suggest that the aim of 7% uncertainty for global solar exposure measurements was not met.

As resources declined in the 1980s the number of station closures increased. From 1987 data recorded by the remaining stations were no longer corrected to climatological estimates and investigations into inconsistency of quality control checks were not possible. By the early 1990s only 6 old network stations were operating, and only monitoring global solar exposure.

Plans were developed to arrest the decline and provide at least 18 ground sites and a satellite system capable of providing complete areal coverage of the Australian region. The upgraded surface network monitoring direct, diffuse and global exposure and terrestrial irradiance was initiated in 1993 and is continuing at this time. Direct spectral transmission measurements (one minute intervals) were added to the Bureau’s solar and terrestrial monitoring sites from 1998.

A station summary of the data available from the Bureau's solar network is available (updated on an intermittent basis only). For more information please send a request via our feedback form.