基于过程模型CROBAS的全局灵敏度分析方法比较

过程机理模型在开发过程中常受限于生理学参数无法直接或准确测量。全局灵敏度分析可以评估模型预测结果对于生理学参数变化的响应,为模型结构改进、数据收集和参数校准提供参考。本研究基于过程模型CROBAS,以华山松为例,选取模型中描述树木结构关系的10个参数,以树高和各器官生物量的Nash-Sutcliffe效率(NSE)为目标函数,比较了3种应用较广泛的全局灵敏度分析方法,即Morris筛选法、基于方差的Sobol指数法和扩展的傅里叶幅度检验法(EFAST)。结果表明: 参数灵敏度排序在不同方法中仅略微有所变化,但对于不同目标函数则区别明显。对算法耗时和收敛效率而言,Morris和EFAST性能较高,Sobol效率相对较低。所有模型输出变量均对单位面积年最大光合速率、比叶面积、消光系数敏感,林冠光截留状态对于林木生长量有着关键性影响,意味着光合固碳量是CROBAS在模型校正和林木生长动态模拟中需要优先进行数据收集、验证与测试的模块。灵敏度分析同时表明,碳平衡理论在林木生物量模拟中最为核心部分是树叶生物量模块的计算与验证。对于复杂过程模型的参数灵敏度分析,如需定性研究可选Morris,而量化评估采用EFAST更适合。

Comparison of global sensitivity analysis techniques based on a process-based model CROBAS

Constructions of process or mechanistic models are limited by physiological parameters,due to difficulty in direct and precise measurement.Global sensitivity analysis could evaluate the response of model outputs to changes in physiological parameters,and provide information for improving model structure,data collection,and parameter calibration.Based on a process model CROBAS,10 parameters related to tree structure of Pinus armandii were selected to compare three widely used global sensitivity analysis methods(the Morris screening method,the variance-based Sobol indices,and the Extended Fourier Amplitude Sensitivity Test(EFAST)),with the objective function formulated by the Nash-Sutcliffe Efficiency(NSE)of tree height and biomass.The results showed that the sensitivity order of parameters slightly varied across different methods,which considerably changed with different objective functions.Both the Morris method and the EFAST method outperformed the Sobol method in terms of time consuming and convergence efficiency.All outputs were sensitive to the maximum rate of canopy photosynthesis per unit area,the specific leaf area,and the extinction coefficient.The light interception of tree canopy played a key role in the simulation of tree growth with CROBAS,suggesting that the module of photosynthetic carbon fixation took priority over any other modules for data collection and model validation during module calibration and tree growth simulation for CROBAS.The calculation and validation of foliage biomass module were crucial when applying carbon balance theory to biomass simulations.In conclusion,for the sensitivity analysis of a complex process-based model,the Morris method was suitable for qualitative studies,while the EFAST method was recommended for quantitative studies.