Topographic effects on the tropical land and sea breeze

The effect of an inland plateau on the tropical sea breeze is modeled using idealized numerical experiments, with a particular emphasis on offshore effects. The parameter space for the calculations is defined by the nondimensional wind speed, a scaled plateau height, and a nondimensional heat source amplitude.

The experiments show that the plateau tends to significantly strengthen the land-breeze part of the circulation, as compared to the case with no terrain. This strengthening of the land breeze is tied to blocking of the sea-breeze density current during the warm phase of the cycle. The blocked sea breeze causes a pool of relatively cold, stagnant air at the base of the plateau, which in turn produces a stronger land breeze density current the following morning. Experiments show that the strength of the land breeze increases with the terrain height, at least for moderate values of height. For very large terrain the sea breeze is apparently blocked entirely, and further increases in terrain height lead to only small increases in land-breeze intensity and propagation.

Details of the flow dynamics are described in terms of the transition from linear to nonlinear heating amplitudes, as well as cases with and without background winds. The results suggest that significant offshore effects in real-world problems are likely tied to nonlinear frontal propagation, and are unlikely to be caused by quasi-linear wave effects.