Vegetated Canopy Heterogeneity Footprints in the Roughness Sublayer

Abstract Turbulent flows over horizontally homogeneous rough surfaces are categorized as rough‐wall boundary layer flows, while flows over homogeneous vegetated canopies are better described through a mixing‐layer analogy. At present, numerous studies have investigated canopy density as a transition mechanism between rough‐wall and mixing‐layer‐type flows. Yet, most considered canopies have been spatially homogeneous, with few exceptions investigating agricultural arrangements. However, most vegetated canopies are not homogeneously distributed, but instead contain gaps and spatial heterogeneities of different scales. In these cases, it remains unclear which are the dominant flow traits, and how spatial heterogeneity affects them. To help overcome these knowledge gaps, this paper aims to characterize flows over vegetated canopies with scales of spatial heterogeneity m randomly distributed, with a uniform under‐canopy roughness and neutral stratification. Large Eddy Simulations of the atmospheric boundary layer with a geostrophic forcing are used. Canopy morphology and heterogeneity are quantified using the non‐dimensional lacunarity metric. Lacunarity is further leveraged to investigate non‐dimensional relations between canopy morphology and traditional turbulence statistics. Furthermore, canopy heterogeneity is investigated as a mechanism to transition from a mixing‐layer‐type flow to a rough‐wall boundary layer flow. Results suggest revised formulations for the and scaling relations to account for the effects of canopy heterogeneity. Results also reveal a novel scaling between the equivalent surface roughness and the canopy heterogeneity parameter , providing a starting point to better understand the role of canopy heterogeneity in atmospheric boundary layer flows.