Solar-induced chlorophyll fluorescence (SIF) has been shown to be a novel proxy for terrestrial gross primary production (GPP). A growing number of ground-based automatic SIF observation systems equipped with hemispherical-conical and bi-hemispherical observation configurations have been developed in synergy with EC flux measurements across different ecosystems. However, the difference in the canopy SIF observed by these two types of configurations has not been well studied, which poses challenges in evaluating their performance in tracking GPP. In this study, we investigated SIF from both hemispherical-conical and bi-hemispherical observation configurations for their ability to track GPP in a maize field during the 2020 growth season. We found that bi-hemispherical SIF observations (SIF_Hemis) showed higher correlations with GPP at both diurnal and seasonal scales, and the superiority of SIF_Hemis for GPP estimation was also supported by Soil-Canopy-Observation of Photosynthesis and the Energy balance (SCOPE) model simulations. In addition, we found that the SIF_Hemis-GPP model established at a satellite overpass time (e.g., 09:30) outperformed the corresponding SIF_Nadir-GPP model in estimating both the half-hourly and daily GPP. The underlying mechanism for the advantage of this SIF_Hemis-GPP relationship was elucidated by a simplified geometrical optical model, which showed that the diurnal patterns of the observed sunlit and shaded leaves for the SIF_Hemis were consistent with those of the canopy GPP. Our study recommends a bi-hemispherical configuration setup for its superiority in monitoring GPP dynamics.

太阳诱导的叶绿素荧光 (SIF) 已被证明是陆地总初级生产 (GPP) 的新代表。越来越多的地面自动 SIF 观测系统配备了半球-圆锥和双半球观测配置，与跨不同生态系统的 EC 通量测量协同工作。然而，这两种配置观察到的冠层 SIF 的差异尚未得到很好的研究，这对评估它们在跟踪 GPP 中的性能提出了挑战。在这项研究中，我们从半球-圆锥和双半球观测配置中调查了 SIF，以了解它们在 2020 年生长季节跟踪玉米田中 GPP 的能力。我们发现双半球 SIF 观测 (SIF _Hemis) 在昼夜和季节尺度上都显示出与 GPP 更高的相关性，并且 SIF _Hemis在 GPP 估计方面的优越性也得到了土壤-冠层-光合作用观测和能量平衡 (SCOPE) 模型模拟的支持。此外，我们发现在卫星立交时间（例如，09:30）建立的SIF _Hemis -GPP模型在估计半小时和每日GPP方面都优于相应的SIF _{Nadir -GPP模型。通过简化的几何光学模型阐明了这种 SIF Hemis} -GPP 关系优势的潜在机制，该模型表明 SIF _{Hemis观察到的阳光照射和阴影叶子的昼夜模式}与冠层 GPP 的一致。我们的研究建议采用双半球配置设置，因为它在监测 GPP 动态方面具有优势。