Idealized Planar Array experiment for Quantifying Surface heterogeneity (IPAQS) provides insight into the role of dispersive fluxes role on the Surface Energy Balance (SEB) closure

Results are presented from the June 2018 Idealized Planar Array experiment for Quantifying Surface heterogeneity (IPAQS) field campaign. The study occurred over the predominantly flat (elevation variation of 1 mkm^-1), smooth (surface roughness, z₀ = 1.1x10^-3 m), and thermally heterogenous (skin temperature variability of 15 K over 100 m distances) SLTEST site at the U.S. Army Dugway Proving Grounds, Southwest of Salt Lake City, Utah. The site was instrumented with a large grid of temporally synchronized, 2-m tall, 3-D sonic anemometers. These sonics were evenly spaced every 200 m over an 800x800-m area, collecting high-frequency windspeed and temperature data. Within the grid, a high-spatial-resolution array of five additional towers were deployed with 10-m spacing. In addition to turbulence measurements recorded in the high-resolution array, the sub-site was equipped with a full Surface Energy Balance (SEB) station. A 28-m tower and thermal camera were deployed adjacent to the grid to provide insight into stability and spatial thermal heterogeneities, respectively. Overall, IPAQS provides a valuable dataset on spatial heterogeneity for numerical weather prediction models, of which are lacking parametrizations to correctly capture the surface energy exchange over heterogeneous surfaces. We hypothesize that the covariance between the time averaged vertical velocity and temperature, known as the dispersive flux, is a valuable component of the surface layer energy exchange over heterogeneous surfaces and could account for up 20% of the SEB during highly unstable periods. The horizontal planar setup of the IPAQS experiment facilitates the computing of dispersive fluxes. Results presented herein provide novel insight into experimentally collected mean and fluctuating variables over a large spatial domain, followed by a discussion of the role of dispersive flux in the closure of the SEB as a function of stability.