Near the tip of Australia’s Northern Territory, Gunn Point is the location for the Darwin ARM Representativeness Experiment, or DARE. This offsite field campaign is obtaining measurements of solar and thermal energy and cloud properties, to compare against similar measurements collected at the permanent ARM site in Darwin, about 25 kilometers to the southwest of Gunn Point. Data collected by instruments at both sites will be compared to help scientists quantify local influences and variability that affect how representative measurements at the Darwin site are compared to the wider area.

The Australian Bureau of Meteorology (BoM) has been operating a weather research site at Gunn Point since 1997. ARM contributed radiometer systems to two other remote sites that were part of the Tropical Warm Pool International Cloud Experiment in 2006, and plans began for a future variability study based at Gunn Point. Recent upgrades to the site infrastructure were made in preparation for a scientific collaboration with Australia’s Commonwealth Scientific and Industrial Research Organization, who are now fielding aerosol and atmospheric composition sampling instruments and a Cimel sunphotometer there. However, it was speculated that shadowing from the nearby C-band polarametric radar (C-POL) might impact the measurements. To test the theory, ARM installed a radiometer system at the site in September 2009, and sure enough; seven weeks of data confirmed the shadowing problem was even more severe than expected.

Between monsoon rains and tropical cyclones typical of summertime Down Under, a new platform is being installed to relocate the Cimel and radiometer system further away from the radar to escape the shadowing. With the radiometer system in place, the DARE campaign will last a minimum of one year. Operations and data continuity, as well as a comparison of results to that point, will then be evaluated to determine whether or not to extend the campaign.