Scales of response of the convective boundary layer to land‐surface heterogeneity

Abstract

The convective boundary layer (CBL) over domains with meso‐γ‐scale (2–20 km) heterogeneity is characterized by preferentially located, organized rolls of characteristic size equivalent to the length‐scale of the heterogeneity. Additionally, random turbulent thermals also develop when the length‐scale of the heterogeneity exceeds 5–10 km. This is due to a complex interaction between the horizontal pressure gradient generated by the heterogeneity and the buoyancy forcing. Consequently, the corresponding wavelet spectrum exhibits two peaks — one representing the turbulent thermals at a characteristic scale of about 1.5 times the CBL height and another denoting the organized eddies at a scale similar to that of the heterogeneity. This implies that subgrid‐scale parameterizations in models with grid size larger than 5–10 km, which account only for random turbulence, are inadequate for heterogeneous domains. Also, this study may provide a more objective classification of scales of atmospheric processes.