Modelling LAI, surface water and carbon fluxes at high-resolution over France: comparison of ISBA-A-gs and ORCHIDEE

[摘要] The Leaf Area Index (LAI) is a measure of the amount of photosyntheticleaves and governs the canopy conductance to water vapor and carbon dioxide.Four different estimates of LAI were compared over France: two LAI productsderived from satellite remote sensing, and two LAI simulations derived fromland surface modelling. The simulated LAI was produced by the ISBA-A-gsmodel and by the ORCHIDEE model (developed by CNRM-GAME and by IPSL,respectively), for the 1994–2007 period. The two models were driven by thesame atmospheric variables and used the same land cover map (SAFRAN andECOCLIMAP-II, respectively). The MODIS and CYCLOPES satellite LAI productswere used. Both products were available from 2000 to 2007 and thisrelatively long period allowed to investigate the interannual and theseasonal variability of monthly LAI values. In particular the impact of the2003 and 2005 droughts were analyzed. The two models presented contrastingresults, with a difference of one month between the average leaf onset datessimulated by the two models, and a maximum interannual variability of LAIsimulated at springtime by ORCHIDEE and at summertime by ISBA-A-gs. Thecomparison with the satellite LAI products showed that, in general, theseasonality was better represented by ORCHIDEE, while ISBA-A-gs tended tobetter represent the interannual variability, especially for grasslands.While the two models presented comparable values of net carbon fluxes,ORCHIDEE simulated much higher photosynthesis rates than ISBA-A-gs(+70%), while providing lower transpiration estimates (−8%).

[学科分类] 地球化学与岩石