Instability Analysis of Terrain-Induced Canopy Flows

Tall vegetation and complex terrain create difficult conditions for measuring and modeling net ecosystem– atmosphere exchanges of carbon, water vapor, and pollutants. The instability of canopy flow regimes over complex terrain is critical for understanding what factors are essential to control exchanges between different canopy flow regimes. In this paper, an analytical criterion of instability of the terrain-induced canopy flows is derived from the simplified thermal-hydromechanical equations by nonlinear instability analysis. The stability of the terrain-induced canopy flows and an oscillation solution are predicted based on the instability criterion. It is found that the critical values of control parameters are determined by the terrain slope, drag coefficient, and leaf area density of vegetation.