Land-Atmosphere Interactions and Mesoscale Circulations in an Idealized Modeling Framework

Many studies have shown that land-atmosphere interactions and feedbacks have important implications for regional climate systems. For instance, clouds and precipitation alter radiation stream profiles, both of which influence land surface fluxes and change the partition between latent and sensible heating. This directly influences boundary layer temperature and moisture regimes and thus subsequent cloud and precipitation formation. Heterogeneous land surface characteristics, due for example to desertification, deforestation, or biomass burning -- all of which occur in Africa -- can also induce mesoscale circulations. Mesoscale circulations spatially impact boundary layer structure and convective initiation. We are investigating these interactions and feedbacks under an idealized framework using the Regional Atmospheric Modeling System (RAMS) version 6.0 and the Land Ecosystem-Atmosphere Feedback (LEAF) model version 3. Several-month simulations have been conducted at convection-resolving scales using periodic boundary conditions and different land surface types representative of surface characteristics in Africa. Results from these idealized simulations will be presented, with a focus on: (1) the influence of land surface properties including albedo, roughness length, soil moisture, and leaf area index on resultant mesoscale circulations and cloudy and precipitating regions; and (2) subsequent feedbacks to surface energy fluxes, shortwave and longwave radiation streams, and heating rates. Preliminary results indicate that both shallower boundary layer and deeper, more elevated mesoscale circulations are present due to the contrasting land surfaces. The circulations vary by season and influence convective development, precipitation, and surface and atmospheric thermodynamic structure. Potential implications for water cycle dynamics in Africa will be discussed.