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

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

Impact of land use/land cover change on regional hydrometeorology in Amazonia

A high‐resolution mesoscale model was used to investigate the impact of deforestation in Amazonia. Coherent mesoscale circulations were triggered by the surface heterogeneity; synoptic flow did not eliminate the circulations but advected them away from the location where they were generated. This was substantiated by satellite‐derived cloud images. These circulations affected the transport of moisture and heat at the synoptic scale and can affect climate. Adequate parameterizations for these processes should be included in GCMs for more accurate climate simulations