Turbulence Characteristics Underneath a Vine Canopy as a Function of Wind Direction and Row Orientation

Turbulent-flow dynamics over agricultural surfaces play an important role in the transport of scalar quantities between the surface and the over-lying surface boundary-layer. For many agricultural crops, row structure is not considered to generally affect turbulence in the surface layer; however, vineyards present a unique case where row spacing and vertical roughness elements are considerably different relative to typical agricultural cropping surfaces. The geometry of a vineyard over the course of a growing season changes with increasing vegetation growth impacting the surface energy balance partitioning and thus affecting vine evaporation amounts. Turbulence has not been extensively investigated in vineyards having relatively large interrow spacing and unique under story architecture. In this study, high frequency turbulence measurements were made of the three dimensional wind components and temperature using sonic anemometers as well as infra-red gas analyzer measurements of water vapor and carbon dioxide above (~5 m) and underneath (0.75 m) a mature vineyard canopy. Both eddy covariance systems were connected to a single data logger to ensure synchronized measurements. Preliminary turbulence statistics are compared and analyzed to assess the interaction of turbulent exchange above and below the vine canopy and to identify periods of intermittency. The results are compared between stable and unstable periods to assess the role of stability in the transport of mass and scalars through the vine canopy system. Ultimately, this research will lead to a better understanding of how to parameterize models of vineyard water, carbon and energy exchange for the unique row spacing and canopy structure of vineyards.