Interaction between wind and temperature fields in the planetary boundary layer for a spatially heterogeneous surface heat flux

Interaction between wind and temperature fields in the planetary boundary layer for a spatially heterogeneous surface heat flux has been investigated using large-eddy simulation. It is shown that a substantial difference exists in the wind and temperature fields, depending on whether the directions of the background wind and the surface heat flux variation are parallel or perpendicular. When they are parallel to each other, two-dimensional plumes induced by the heterogeneous surface heat flux are easily destroyed by the background wind, and the velocity field is strongly modified by convective eddies compared to the case when they are perpendicular to to each other. This leads to a substantial difference in the profiles of turbulent kinetic energy and its flux. It also results in a difference between the two cases in the bulk properties of the planetary boundary layer, such as the entrainment at the top of the planetary boundary layer and the drag at the bottom, which have important implications for boundary-layer modelling. The difference between the two cases exists even when the background wind speed is as large as 15.0 m s^-1. Meanwhile, the contrast between two cases is weakened by the Coriolis force.