Overview of the Bureau's solar observation program

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, but using modest quality black-only Middelton EP07 thermopile pyranometers.

The combined network relied on initial calibration of the pyranometers, and subsequent correction of data 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, by the mid-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 a network of high quality 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 continues to operate, although the number of open stations at any one time has fluctuated over the years. Most recently, eight stations were opened for a limited time as part of a collaborative project with Geoscience Australia.

Daily estimates of global solar exposure derived from satellite images exist from 1990. Satellite-derived estimates are based on images from the Geostationary Meteorological Satellites GMS-4 and GMS-5, Geostationary Operational Environmental Satellite (GOES-9), and the MTSAT-1R and MTSAT-2 satellites, which are provided with permission of the Japan Meteorological Agency (JMA) and the United States National Oceanic & Atmospheric Administration (NOAA).

Monthly climatologies of hourly global and direct beam solar exposure were first produced in 2009 for the Australian Renewable Energy Atlas (no longer operational). The underlying hourly spatial data became publically available in 2010. Work continues within the Bureau to enhance the computer model and associated data processing, as well as integration of Himawari-8 data which became operational in 2015.