Study of turbulence behavior above two different crops

Abstract

Turbulence structures are studied for momentum and sensible heat fluxes above different crops, maize and soybean, under neutral and unstable regimes through quadrant analysis. Micrometeorological sensors were installed at the same height (5 m) over productive plots in Buenos Aires province, Argentina. The effect of variations in crop height (in relation to sensor height) throughout the growing season is studied. In the maize experiment, canopy mixing-layer conditions prevail, with strong unstable situations, where a more efficient sensible heat transport relative to that of momentum follows a pattern explained by thermal plume type structures. Ejections are more intense but sweeps dominate in time for sensible heat transport. In addition, sweeps dominate both in intensity and time for momentum flux, due to the closeness of measurements to the canopy top. Above soybean, surface layer behavior is identified with near-neutral conditions, and there is a flux transport pattern associated with hairpin vortex type structures. Sensible heat and momentum fluxes are driven by the same motions, with no clear differences in transport efficiency. In soybean, ejections are more important because of a higher distance of measurement height to the canopy top. For each experiment, turbulence vary mainly due to atmospheric stability, while the effect of variation in the distance between the sensor and the top of the canopy due to plant growth is negligible. In this work, turbulence interactions in the surface layer are identified at heights that are not studied by works based on LES simulations.