Abstract -
The large-scale climate plays an important role in controlling the distribution of vegetation on the land surface. However, changes in vegetation can also modulate the large-scale climate system. Vegetation controls many physical properties of the land surface, including albedo, aerodynamic roughness, and how hard it is to evaporate water. Each of these surface properties modulates the flux of energy and water between the land and the atmosphere in different ways. The atmosphere can respond to changes in energy fluxes from the land surface, through changes in temperature, cloud cover, rainfall, and even through large-scale shifts in atmospheric circulation. Here, we present results from an idealized modelling study where we isolate the effect of individual land surface properties on (i) surface climate and (ii) large-scale atmospheric circulation. In certain regions, land surface properties have a large control on the atmosphere - in others, not so much! In this talk, we will explore which surface properties matter where, and why the atmosphere cares (or doesn't) about changes in these land surface properties.
Changes in terrestrial evaporation play the largest impact on surface temperatures in regions where clouds are highly sensitive to latent heat flux from the land surface. Decreases in terrestrial albedo generate global-scale warming not only by causing more shortwave radiation to be absorbed at the surface, but also by triggering feedbacks in snow, ice, cloud cover, atmospheric temperatures, and water vapour. Changes in land surface properties induce large-scale shifts in atmospheric circulation by modifying the top of atmosphere energy budget. Leveraging atmospheric radiative kernels, we use modelled changes in the top of atmosphere energy budget and the relationship between atmospheric heat transport and the latitude of the ITCZ to decompose annual mean shifts in the ITCZ into the portion attributable directly to the imposed change in the land surface, and the portion attributable to individual atmospheric feedbacks.
