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Quasi-two-dimensional roll vortices are frequently observed in hurricaneboundary layers. It is believed that this highly coherent structure, likelycaused by the inflection-point instability, plays an important role inorganizing turbulent transport. Large-eddy simulations are conducted toinvestigate the impact of wind shear characteristics, such as the shearstrength and inflection-point level, on the roll structure in terms of itsspectral characteristics and turbulence organization. A mean wind nudgingapproach is used in the simulations to maintain the specified mean wind shearwithout directly affecting turbulent motions. Enhancing the radial wind shearexpands the roll horizontal scale and strengthens the roll's kinetic energy.Increasing the inflection-point level tends to produce a narrow and sharppeak in the power spectrum at the wavelength consistent with the roll spacingindicated by the instantaneous turbulent fields. The spectral tangentialmomentum flux, in particular, reaches a strong peak value at the rollwavelength. In contrast, the spectral radial momentum flux obtains itsmaximum at the wavelength that is usually shorter than the roll's, suggestingthat the roll radial momentum transport is less efficient than the tangentialbecause of the quasi-two-dimensionality of the roll structure. The mostrobust rolls are produced in a simulation with the highest inflection-pointlevel and relatively strong radial wind shear. Based on the spectralanalysis, the roll-scale contribution to the turbulent momentum flux canreach 40 % in the middle of the boundary layer

Impact of vertical wind shear on roll structure in idealized hurricane boundary layers