Effects of the Coriolis force on the coherent structures in conventionally neutral atmospheric boundary layers

TL;DR

This study uses large-eddy simulation to explore how the Coriolis force influences turbulent coherent structures in neutral atmospheric boundary layers, revealing deflection patterns and inclination angle changes related to latitude and geostrophic wind.

Contribution

It demonstrates the impact of the Coriolis force on turbulent structures and proposes a universal relationship for their deflection in the atmospheric boundary layer.

Findings

Coriolis force causes coherent structures to deflect toward the geostrophic wind direction.

The structure deflection angle can be collapsed onto a universal curve based on wind veer.

Inclination angles of turbulent structures increase with decreasing latitude or increasing geostrophic wind.

Abstract

It is well known that the Coriolis force due to Earth's rotation can induce wind veer in the mean flow velocity of an atmospheric boundary layer (ABL), but much less is known about its effects on turbulent coherent structures. In this work, large-eddy simulation (LES) is employed to investigate the effects of the Coriolis force on the characteristics of turbulent coherent structures in the conventionally neutral atmospheric boundary layers (CNBL). Variation of the Coriolis force is realized by changing latitude or geostrophic wind speed.We found that the Coriolis force causes distinct deflection of coherent velocity structures to the geostrophic wind direction, which is not aligned with the direction of either the mean wind or the mean shear. By plotting against the difference between the local wind veer angle and the global cross-isobaric angle, the structure deflection angle under different conditions can be well collapsed, indicating a possible universal relationship. Moreover, we also studied the effect of the Coriolis force on the inclination angle of large-scale turbulent structures. It is found that as latitude decreases or geostrophic wind speed increases, the inclination angle in the surface layer increases, probably due to the deflection of turbulent structures caused by the Coriolis force.