Convective boundary-layer structure in the presence of wind-following swell

†The contribution of this author to this article was prepared as part of his official duties as a US Federal Government employee. Themarine boundary layer is known to be influenced by fast long ocean swell waves travelling away from their generation area, where they were initiated by momentum transferred to the ocean wave field during storms. The atmospheric boundary layer during wind-following swell and various stability states has been investigated using large-eddy simulation (LES) data. The dominant energy-containing motions in the near-neutral atmospheric boundary layer over flat terrain are known to be dominatedbynear-ground shear-induced regions of high- and low-speedflow.Wind fields and momentum fluxes from LES for swell-dominated situations have been used to interpret field measurements suggesting that these motions are disrupted by effects related to the underlying wave field in the presence of swell waves. Statistical analysis and visualization are used to further describe the effects of stratification during swell for convective boundary-layer winds and fluxes. A mechanism for transport of momentum to the upper levels of the boundary layer is suggested from interpretationof LESdata.Coherent detached eddies from thedirectlywave-induced motions near the surface are found to maintain an upward momentum transfer. This mechanism is found to strengthen during stronger swell conditions and also during slightly convective conditions. In this way, it is argued that processes related to both the wave field and surface convection can have a significant influence on the global structure of neutral and convective boundary layers during swell. This has implication for the turbulence length-scales during wind-following swell. Copyrigh