Effects of land-conversion in a biosphere–atmosphere model of Northern South America – Part 1: Regional differences in hydrometeorology

Abstract. This work investigates how landuse changes over northern South America, driven by human interventions, have affected the regional patterns of hydrology. Comparisons are made to scenarios where no human disturbance of the regional vegetation is assumed. A numerical model of the terrestrial biosphere (Ecosystem Demography Model 2 – ED2) is combined with an atmospheric model (Brazilian Regional Atmospheric Modeling System – BRAMS) to investigate how land conversion in the Amazon and Northern South America have changed the hydrology of the region. Two numerical realizations of the structure and composition of terrestrial vegetation are used as boundary conditions in a simulation of the regional land surface and atmosphere. One realization seeks to capture the present day vegetation condition that includes deforestation and land-conversion, the other is an estimate of the potential structure and composition of the region without human influence. Model output is assessed for consistent and significant pattern differences in hydrometeorology. Results show that South American land conversion has a consistent impact on the regional patterning of precipitation. Land-conversion was not associated with a significant bias in continental mean precipitation, but was associated with a negative bias in mean continental evaporation and a positive bias in continental runoff. A companion paper continues this analysis, with case studies that focus on specific areas that show significant differential hydrologic response.