Simulation of Surface Fluxes in Two Distinct Environments along a Topographic Gradient in a Central Amazonian Forest using the INtegrated LAND Surface Model

Abstract. The Integrated Land Surface model (INLAND) land surface model, in offline mode, was adjusted and forced with prescribed climate to represent two contrasting environments along a topographic gradient in a central Amazon Terra Firme forest, which is distinguished by well-drained, flat plateaus and poorly drained, broad river valleys. To correctly simulate the valley area, a lumped unconfined aquifer model was included in the INLAND model to represent the water table dynamics and results show reasonable agreement with observations. Field data from both areas are used to evaluate the model simulations of energy, water and carbon fluxes. The model is able to characterize with good accuracy the main differences that appear in the seasonal energy and carbon partitioning of plateau and valley fluxes, which are related to features of the vegetation associated with soils and topography. The simulated latent heat flux (LE) and net ecosystem exchange of carbon (NEE), for example, are higher on the plateau area while at the bottom of the valley the sensible heat flux (H) is noticeably higher than at the plateau, in agreement with observed data. Differences in simulated hydrological fluxes are also linked to the topography, showing a higher surface runoff (R) and lower evapotranspiration (ET) in the valley area. The different behavior of the fluxes on both annual and diurnal time scales confirms the benefit of a tiling mechanism in the presence of large contrast and the importance to incorporate subgrid-scale variability by including relief attributes of topography, soil and vegetation to better representing Terra Firme forests in land surface models.