A previous Doppler-lidar observation near a sea-breeze front revealed that small-scale vertical vortices, similar to dust devils, have a preferred direction of rotation, which suggests that their rotation was affected by meso-scale vertical vorticity associated with the front. In contrast, planetary vorticity is believed to have a negligible effect on dust devils. This paper investigates the effects of ambient rotation on dust devils by means of a large eddy simulation, which yielded the following findings: when the ambient rotation is as small as the earth's rotation, only a tiny asymmetry is found in the occurrences of vertical vortices of different signs; as the ambient rotation is increased, it significantly affects the rotational direction of the vortices, and the magnitude of their vertical vorticity attains a maximum for an ambient vorticity of about 10-3 s-1; a further increase in the ambient rotation changes the structure of convection in the convective mixed layer and suppresses horizontal convergence, so that vertical vorticity of the vortices is reduced.
ASJC Scopus subject areas
- Atmospheric Science