Use of agricultural statistics to verify the internannual variability in land surface models: a case study over France with ISBA-A-gs
1CNRM/GAME, Météo-France, CNRS, URA 1357, 42 avenue Coriolis, 31057 Toulouse Cedex 1, France
2Météo-France, Direction de la Production, 42 avenue Coriolis, 31057 Toulouse Cedex 1, France
3Ecologie et Ecophysiologie Forestière, INRA, UHP, Nancy, France
4Unité 1106 Infosol, INRA, Orléans, France
Abstract. In order to verify the interannual variability of the above-ground biomass of herbaceous vegetation simulated by the ISBA-A-gs land surface model, within the SURFEX modelling platform, French agricultural statistics for C3 crops and grasslands were compared with the simulations for the 1994–2008 period. While excellent correlations are obtained for grasslands, representing the interannual variability of crops is more difficult. It is shown that, the Maximum Available soil Water Capacity (MaxAWC) has a large influence on the correlation between the model and the agricultural statistics. In particular, high values of MaxAWC tend to reduce the impact of the climate interannual variability on the simulated biomass, and to allow the simulation of a negative trend in biomass production, in relation to a marked warming trend, of about 0.12 Ky−1 on average, affecting the daily maximum air temperature during the growing period (April–June), especially in northern France. The estimates of MaxAWC for C3 crops and grasslands, currently used in SURFEX, are about 129 mm and do not vary much. Therefore, more accurate grid-cell values of this parameter are needed.