A continental instrumented ground site network (CIGSN, Australia): a prerequisite for the detection, interpretation and quantification of global change

It is recognised that one of the steps limiting the development of an improved understanding of both physical and biological processes at the land surface is access to time series of precision validated surface variables derived from satellite (and surface) data. Existing satellite data archives contain inconsistencies generated by atmospheric conditions and by sensor drift. These two factors confound analysis and limit the use of these data for monitoring the impact of climatic or anthropogenic change on the status or functioning of terrestrial ecosystems. This paper reports on a project (CIGSN) that directly addresses the issue of the precision validation of satellite observations of the continental land surface. It was initially devised and implemented for the precision calibration of AVHRR data at two sites: Walpeup (surface temperature) and Hay (surface temperature and albedo). These two sites will be increased to ∼10 to achieve continental coverage over the next three years to expand the capacity with which optical and thermal observations (TM, MSS, AVHRR, ATSR, SPOT, SPOT4 Vegetation Instrument) can be precision validated prospectively, or new models of derived variables (e.g. net radiation) validated. As well it is possible to retrospectively precision calibrate AVHRR data for 12 years and Landsat MSS data for 20 years.