The Southwest Australian Bunny Fence Experiment
Udaysankar S. Nair, Univ. of Alabama, Huntsville, AL; and T. J. Lyons, J. Hacker, R. M. Welch, R. A. Pielke, S. Asefi, and Y. Wu
In Southwest Australia, over the last few decades, areas in excess of 13 million hectares have been cleared of native vegetation for cultivation of winter growing agricultural crops. A vermin proof fence (“Bunny Fence”, also often called “Rabbit Fence”), approximately 750 km long, separates the agricultural areas to the west from the native vegetation areas to the east. Significant differences in albedo between the native vegetation and agricultural areas are readily visible in satellite imagery with the agricultural areas having a higher albedo compared to native vegetation. The drastic nature of land use change, coupled with relatively small variations in topography makes this area ideal to investigate the influence of land use and landscape heterogeneity on atmospheric circulation and cloud formation. Indications of an influence of land use on atmospheric processes is readily seen in satellite imagery which show very characteristic cloud formation patterns where boundary layer clouds form preferentially over the native vegetation areas with the western boundary of the cloud fields often coinciding with the Bunny Fence.
The Bunny Fence Experiment (BuFex) 2005, 2006 and 2007, a series of field campaigns conducted jointly by the University of Alabama in Huntsville, Murdoch University, and Flinders University, has been designed to study the impact of human induced regional-scale landscape modification on atmospheric circulation and cloud formation in southwest Australia. The first phase of the field campaign, BuFex-05, was conducted from 1-20 of December of 2005. During BuFex-05 measurement of atmospheric thermodynamic profiles and surface energy fluxes, surface meteorological variables, soil temperature and soil moisture were made at two sites: one located at the Lake King airstrip 20 km to the west of the Bunny Fence and the other located 20 km to the east of the Fence in the Frank Hann National Park. Radiosondes were released simultaneously from both the sites approximately every four hours during the day. On selected days, Flinders University's Small Environmental Research Aircraft (SERA), an instrumented ECO-Dimona, flew transects between the two sites measuring air temperature, humidity, and sensible, latent heat and momentum fluxes. The SERA also operated an infrared, three channel visible scanner and a laser altimeter. The ASTER sensor on the NASA EOS Terra satellite platform acquired multiple scenes over the study region during the field experiment. Detailed analysis of the data collected during the BuFex-05 is being conducted. Initial analysis show differences in boundary layer heights between the sites, with deeper boundary layer over the native vegetation side during synoptically calm days. This paper will present a detailed overview of the BuFex-05 and present some of the preliminary results..
Joint Session 1, Impacts of Terrestrial Changes on Weather and Climate (Joint with 21st Conference on Hydrology and Climate Aspects of Hydrometeorology)
Tuesday, 16 January 2007, 8:30 AM-12:00 PM, 214A
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