The convective boundary layer (CBL) over domains with meso-&ggr;-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. ¿ 2000 American Geophysical Union