Linear Mountain Waves in Flow Past a Mountain Range with Concavity and Convexity

The interaction of airflow with mountain ranges in a stable atmosphere generates internal gravity waves, leading to wind deceleration on the windward side and acceleration on the lee side. Recent studies have explored airflow over the bended mountain range, characterized by convexity on the windward side and concavity on the lee side. In this study, we have computed linear analytic solutions for three-dimensional mountain waves over such terrains, and examined the surface winds (u and v), and horizontal divergence.

Our analysis reveals that when the terrain features convexity on the windward side and concavity on the lee side, surface wind speed amplifies within the area of concave region through the low-level convergence. In the bell-cosine mountain range, the maximum downslope wind exceeds that predicted by the analytic linear solution for the two-dimensional bell-shaped mountain range (U + NH/2). However, it does not surpass the maximum wind observed for the 2-dimensional bell-cosine mountain range. The presence of the convex bend in the mountain range yields flow splitting in the upwind side and does not promote downslope wind and wave breaking.

The presence of concavity in the lee side amplifies the downslope wind by low level convergence in the lee side and convexity in the windward side of a mountain range has the potential to enhance downslope winds when the terrain slope becomes asymmetric. Our findings shed light on the potential enhancement of downslope winds in mountain ranges exhibiting such terrain features.