Validating regional-scale surface energy balance models

One of the major challenges in developing reliable regional surface flux models is the relative paucity of scale- appropriate validation data. Direct comparisons between coarse-resolution model flux estimates and flux tower data can often be dominated by sub-pixel heterogeneity effects, making it difficult to assess the intrinsic model accuracy. Several possible approaches to validating regional energy balance models are presented, including using high-resolution remote sensing data to disaggregate to the observation scale, or alternatively using dense tower networks or aircraft-based flux sensors to improve the spatial coverage of the observations. Such techniques, however, typically have limited temporal coverage, often providing only snapshots of surface conditions. Scintillometry provides a unique means for acquiring time-continuous flux measurements at the scale of the regional model pixel, facilitating rigorous validation over heterogeneous landscapes. Paired short- and microwave scintillometers allow simultaneous measurement of area-averaged sensible and latent heating, and will be invaluable in working towards robust continental and ultimately global models of the surface energy balance.