Terrestrial biosphere models (TBMs) often adopt the Farquhar biochemical model coupled with the Ball-Berry stomatal conductance () model to simulate ecosystem carbon and water fluxes. The parameters , representing the sensitivity of to the photosynthetic rate, and , representing the leaf photosynthetic capacity, are two pivotal parameters but the two main sources of uncertainties in TBM simulations. The temporal variations of in TBMs are still elusive, due to the lack of direct observations. It also remains unclear how accurate estimates of and can improve the simulations of carbon and water fluxes. In this study, we used a Bayesian parameter optimization approach to estimate seasonally varying and from eddy covariance observations in a mixed forest stand at the Borden Forest Research Station located in southern Ontario, Canada and used in-situ observations of and for validation. Three strategies were tested for optimizing and , including the carbon, water, and carbon-water coupling scenarios. and optimized from carbon-water coupling constraints shows best correlations with the measured (R = 0.70) and (R = 0.70). By incorporating optimized and with seasonal variations, we found considerable improvements in the estimated gross primary productivity (GPP) and evapotranspiration (ET) compared with constant and , with R increasing from 0.78 to 0.85 for GPP, from 0.65 to 0.71 for ET and RMSE reducing from 2.579 g C to 2.038 g C for GPP, from 1.151 mm to 0.137 mm for ET. This study proposes an effective approach to retrieve and for TBMs and demonstrates the efficacy of incorporating seasonally variable and for reducing the uncertainties in GPP and ET simulations, which supports accurate quantifications of land-atmosphere exchanges.

中文翻译：

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基于联合碳水通量约束优化季节性变化的光合参数

陆地生物圈模型（TBM）通常采用Farquhar生化模型与Ball-Berry气孔导度（）模型相结合来模拟生态系统碳和水通量。参数 代表对光合速率的敏感性， 和 代表叶片光合能力，是两个关键参数，也是 TBM 模拟中不确定性的两个主要来源。由于缺乏直接观察，TBM 的时间变化仍然难以捉摸。目前还不清楚如何准确估计和改进碳和水通量的模拟。在这项研究中，我们使用贝叶斯参数优化方法来估计加拿大安大略省南部博登森林研究站混合林中的季节变化和涡度协方差观测，并使用现场观测和验证。测试了三种策略来优化 和 ，包括碳、水和碳-水耦合场景。并根据碳-水耦合约束进行优化，显示出与测量值 (R = 0.70) 和 (R = 0.70) 的最佳相关性。通过将优化的 和 与季节变化相结合，我们发现与常数 和 相比，估计的总初级生产力 (GPP) 和蒸散量 (ET) 有相当大的改善，其中 GPP 的 R 从 0.78 增加到 0.85，ET 和 RMSE 的 R 从 0.65 增加到 0.71 GPP 从 2.579 g C 到 2.038 g C，ET 从 1.151 mm 到 0.137 mm。本研究提出了一种有效的 TBM 检索方法，并证明了纳入季节性变量以及减少 GPP 和 ET 模拟中的不确定性的有效性，这支持了陆地-大气交换的准确量化。