Sensitivity analysis of the rice model WARM in Europe: Exploring the effects of different locations, climates and methods of analysis on model sensitivity to crop parameters

Sensitivity analysis studies how the variation in model outputs can be due to different sources of variation. This issue is addressed, in this study, as an applicationof sensitivity analysis techniques to a cropmodel in the Mediterranean region. In particular, an application of Morris and Sobol’ sensitivity analysis methods to the ricemodelWARM is presented. The output considered is aboveground biomass atmaturity, simulated at five rice districts of different countries (France, Greece, Italy, Portugal, and Spain) for years characterized by low, intermediate, andhigh continentality. The total effect indexof Sobol’ (that accounts for the total contribution to theoutputvariationdueagivenparameter) and twoMorris indices (meanm and standarddeviationsof the ratios output changes/parameter variations) were used as sensitivitymetrics. Radiation use efficiency (RUE), optimum temperature (Topt), and leaf area index at emergence (LAIini) ranked in most of the combinations site year as first, second and third most relevant parameters. Exceptions were observed, depending on the sensitivitymethod (e.g. LAIini resulted not relevant by theMorrismethod), or site-continentality pattern (e.g. with intermediate continentality in Spain, LAIini and Topt were second and third ranked; with low continentality in Portugal, RUE was outranked by Topt). Low s values associated with the most relevant parameters indicated limited parameter interactions. The importance of sensitivity analyses by exploring site climate combinations is discussed as pre-requisite to evaluate either novel crop-modelling approaches or the application of known modelling solutions to conditions not explored previously. The need of developing tools for sensitivity analysis within the modelling environment is also emphasized. 2009 Elsevier Ltd. All rights reserved.