Abstract
The surface energy budget at the earth surface describes the partitioning of energy into storage (S), sensible heat (H), and latent heat (LE). The measurement of the surface energy flux provides key insight into processes such as evapotranspiration (ET) and the water budget. However, attempts to measure energy fluxes into these variables often fail to account for all the available energy, referred to as energy balance closure error (EBCE). Available energy (net radiation - Rn) and energy fluxes into S, H, and LE were analyzed for a lodgepole pine forest in eastern Idaho, USA. The EBCE analysis indicated approximately 20% missing energy for the lodgeplole pine forest. All flux pathways were evaluated to identify which were under-measured. Consistent with findings at other flux measurement sites, it is believed that H and LE were under-measured. A novel approach to adjust apparently under-measured H and LE from eddy covariance (EC) systems was developed using independently-measured H from a large aperture scintillometer (LAS) based on the hypothesis that LAS would not be subject to the same errors that affect EC measurements, namely unmeasured fluxes associated with the low frequency part of the turbulent spectra caused by landscape heterogeneity, advection, and non-steady state conditions. Adjusted data was then used to evaluate ET for the lodgepole pine forest and to develop a Kc curve for the forest based on reference ET (ETr) using meteorological data from a nearby weather station.