Comparison of Turbulent Statistics and Spectral Characteristics Under Strong Advective Conditions.

Understanding the turbulent exchange of mass and energy from a surface remains essential to appropriately characterize and quantify the components of surface energy balance. This is particularly true for semi-arid agricultural surfaces that experience significant advection in conjunction with large spatial and temporal variations in the partition of the surface energy balance. Under highly unstable conditions, the physical turbulent exchange processes at a surface significantly deviate from fundamental assumptions associated with eddy covariance (EC) measurements of mass and energy. At the Bushland Evapotranspiration and Agricultural Remote Sensing Experiment (BEAREX_08) intensive field campaign conducted during the summer of 2008, nine EC systems were deployed over irrigated and non-irrigated crop, pasture and grassland locations. Additional instrumentation was deployed on a 10 m tower to measure the quasi-mixed layer above the surfaces. All of the instrumentation systems acquired data at a frequency of 20 Hz. Power and co-spectra analysis were calculated using the complex Fast Fourier Transform (FFT) for the u, v, and w components of velocity and scalar values of T and q concentrations. Additional analysis will include the impact of strong advection conditions on tests for stationarity (trend) conditions and integral turbulence characteristics following Foken and Wichura, 1996.