Improving the ISBA(CC) land surface model simulation of water and carbon fluxes and stocks over the Amazon forest

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Joetzjer, E. | Delire, Christine | Douville, Hervé | Ciais, Philippe | Decharme, Bertrand | Carrer, Dominique | Verbeeck, H. | de Weirdt, M. | Bonal, Damien

Edité par CCSD ; European Geosciences Union -

International audience. We evaluate the ISBA CC (Interaction Soil Bio-sphere Atmosphere Carbon Cycle) land surface model (LSM) over the Amazon forest, and propose a revised param-eterization of photosynthesis, including new soil water stress and autotrophic respiration (R A) functions. The revised version allows the model to better capture the energy, water and carbon fluxes when compared to five Amazonian flux towers. The performance of ISBA CC is slightly site dependent although similar to the widely evaluated LSM ORCHIDEE (Organizing Carbon and Hydrology In Dynamic Ecosystems – version 1187), which is based on different assumptions. Changes made to the autotrophic respiration functions, including a vertical profile of leaf respiration, lead to yearly simulated carbon use efficiency (CUE) and carbon stocks which is consistent with an ecophysiological meta-analysis conducted on three Amazonian sites. Despite these major improvements , ISBA CC struggles to capture the apparent sea-sonality of the carbon fluxes derived from the flux tower estimations. However, there is still no consensus on the season-ality of carbon fluxes over the Amazon, stressing a need for more observations as well as a better understanding of the main drivers of autotrophic respiration.

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