Idealised numerical simulations of aerodynamic roughness length effects on sea breeze characteristics

A two-dimensional hydrostatic meso-gamma-scale model was used to study possible effects of a step change in roughness on the daytime sea breeze. Idealised numerical simulations with the length of aerodynamical roughness (z(0)) ranging from 0.05 m to 1.0 m and by an increase of 0.05 m in all land grid points were made. Two z(0) effects could be pointed out: an increase in the mixing process and a reduction in the wind speeds in the surface layer. An increase of both heights and magnitudes of the sea breeze circulation, caused by a vertical extension of the turbulent field, followed a faster inland penetration of the sea breeze. The second effect resulting from a successive increase in z(0) values was a retardation of the sea breeze front near the ground, visible in its slope. This effect allowed the already faster inland penetration of the marine air high above the land.