Surface Roughness Variations control the Regional Atmospheric Response to Contemporary Deforestation in Rondônia, Brazil

Abstract:

The net atmospheric response to deforestation is known to be a combination of individual atmospheric processes and their interactions triggered by changes in various land surface characteristics. These individual responses also vary with the scale of deforestation. Previous studies of atmospheric impacts of Amazonian deforestation have focused on very small (~1 km) and very large (hundreds of km) scales of deforestation and have showed that different land surface properties can dominate the atmospheric response at different scales. However, analysis of the net atmospheric impact of intermediate-scale deforestation (tens of km) has received less attention, despite it being a better representative of the contemporary landscape in some parts of the Amazon. This study looks at the effects of contemporary intermediate-scale deforestation in Rondônia, Brazil, with an emphasis on the role of changes in surface roughness, using a variable-resolution GCM, the Ocean-Land-Atmosphere Model. It is found that reductions in surface roughness give rise to a mesoscale circulation that is capable of convective triggering but that weakens the turbulent energy fluxes between land and atmosphere. Overall, this mesoscale circulation causes distinct impacts on the hydroclimates of the western and eastern halves of Rondônia, increasing convection in the former while suppressing it in the latter. These results show that the regional atmospheric response to contemporary intermediate-scale deforestation in Rondônia is likely to be more influenced by differences in surface roughness between forest and forest clearings than by the differences in the surface energy partitioning which is the dominant factor at small scales of deforestation.