Surface Energy Budget Closure in Sagebrush Landscape

The eddy-covariance technique was used to measure the components of the surface energy budget at 30-minute means for two eddy covariance tower sites located in Birch Creek Valley, Idaho from June 24, 2013 to September 15, 2013. The two towers were located eight miles apart north-south on opposite sides of the valley. The differing factors between the two sites were the distributions and concentrations of the sagebrush in each area, the elevation above sea level of the towers, and the terrain undulations. The surface energy budget consists of four main components: latent heat flux (LE), sensible heat flux (H), ground heat flux (G), and net radiation (Rn). In ideal situations net radiation equals the sum of the latent, sensible, and ground heat flux values causing the energy budget to “close” (i.e., Rn=H+LE+G). When calculating the ground heat flux, corrections were made to account for needing to bury soil sensors at a deep enough depth so they are not significantly disturbed and the absolute depth in the soil is not significantly altered due to erosion, compaction or expansion of the soil layer. Meteorological and turbulent variables were analyzed during periods where the surface energy budget was closed in an attempt to determine the main factors that contributed to surface energy budget closure. Meteorological and turbulent variables were also analyzed in instances where the surface energy budget was not closed. One instance of particularly high closure rates was identified from August 15, 2013 to August 19, 2013 and analyzed extensively.