11.4 Turbulence Profile Characteristics over a Mature Vineyard

Thursday, 15 May 2014: 11:15 AM
Bellmont A (Crowne Plaza Portland Downtown Convention Center Hotel)
John H. Prueger, USDA-ARS, Ames, IA; and J. G. Alfieri, W. P. Kustas, L. E. Hipps, L. G. McKee, M. C. Anderson, and J. L. Hatfield

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 than typically found in typical agricultural crops. 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 been extensively investigated over many over agricultural surfaces for horizontally uniform canopies, but agricultural systems having much larger interrow spacing such as vineyards have not been adequately investigated. In this study, high frequency vertical profile turbulence measurements of wind components u, v, w and T using sonic anemometers over a mature vineyard were conducted for different temporal and vegetative conditions. Additionally the impact of row structure on the wind dynamics is also investigated over a range of wind direction and stability conditions. Spectral analysis results for various conditions of vegetative stage growth, surface layer stability and temporal periods representing spring, mid-summer and early fall conditions are investigated for three heights above the vine canopy. Preliminary results provide insight into turbulence characteristics at several heights in the surface layer above the vineyard as affected by vine structure and spacing, wind speed, direction and stability.
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