生态过程模型已经被广泛用于模拟总初级生产力(Gross Primary Productivity,GPP)和蒸散发(Evapotranspiration,ET).本研究使用 BEPS(Biosphere-atmosphere Exchange Process Simulator)模型两个不同时间尺度的版本,即日步长(BEPS-Daily)和小时步长(BEPS-Hour-ly),比较两种模型模拟结果的差异,并分析误差来源.结果表明:1)叶面积指数(Leaf Area Index,LAI)是驱动陆地生态系统模型的重要植被结构参数.BEPS-Daily模拟的阳叶LAI会大于BEPS-Hourly,而模拟的阴叶LAI会更小;2)植被的气孔控制着CO2 和水汽的交换,气孔导度表征气孔对环境因子的响应程度.BEPS-Daily计算的气孔导度对环境因子的敏感度高于BEPS-Hourly.因此,当受到辐射、气温以及土壤水分等环境因子的限制时,BEPS-Daily模型计算得到的气孔导度会出现低估的情况,这会导致BEPS-Daily模拟的GPP 和蒸腾也出现了低估的模拟值;3)总体来说,两模型的模拟精度差别不大,BEPS-Hourly的模拟精度略高,而BEPS-Daily则具备更高的运算效率,因此,在应用中可根据实际需求选择模型.
Analysis of Differences in BEPS Model Simulations at Different Time Scales
Ecological process models have been widely used to simulate gross primary productivity(GPP)and evapotranspiration(ET).This study uses two different time step versions of the BEPS(Biosphere-atmosphere Exchange Process Simulator)model,the daily time step(BEPS-Daily)and the hourly time step(BEPS-Hourly),to compare the differences in simulated results between the two models and analyze the sources of errors.The results show that,1)leaf area index(LAI)is an important vegetation structural parameter driving terrestrial ecosystem models.The simulated sunlit LAI by BEPS-Daily is larger than BEPS-Hourly,while the simulated shaded LAI is smaller.2)Plant stomata control the exchange of CO2 and water vapor.Stomatal conductance characterizes the sensitivity of stomata to environmental factors.The stomatal conductance calculated by BEPS-Daily is more sensitive to environmental factors than BEPS-Hourly.Therefore,when constrained by environmental factors such as radiation,air temperature and soil moisture,the stomatal conductance calculated by BEPS-Daily model tends to be underestimated,which leads to underestimation of GPP and transpiration simulated by BEPS-Daily.3)Overall,the simulation accuracy between the two models is similar,with BEPS-Hourly being slightly more accurate,while BEPS-Daily has higher computational efficiency.Therefore,we can choose the model according to actual needs in applications.
carbon and water cycleBEPS modelLAIstomatal conductance
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