## 3 Results  
### Reconciliation of Time-Series Phenological Characteristics with Crop Growth Stages  
As discussed earlier, there exists a gap between the transitions identified in the smoothed and model-fitted phenological curve and the actual crop physiological growth stages [66]. To bridge this gap, a reconciliation step is imperative to establish the mapping relationship between these two datasets before proceeding with accuracy assessment and further comparisons. In this study, the range of each estimated transition dataset was visualized and compared with the distribution of ground-based observations of crop growth stages (refer to Figures 3 and 4). If the majority of ground-based observations fall in the range of a specific transition date (e.g., the SOS in the TR method), it is highly likely that this crop growth stage aligns with the identified transition date and vice versa. This comparative analysis allows us to establish potential mapping relationships between transition dates and crop growth stages, which will be subject to further assessment. In Figures 3 and 4, the distinction between precision and accuracy in estimation is illustrated. Taking Figure 3a as an example, the SOS, POS and EOS extracted by the TR method span from approximately DOY 185 to 200, 205 to 225 and 245 to 255, respectively. Each set of these transition dates exhibits a high degree of precision, indicating a very narrow time span. However, notably, the first three growth stages (SOW, VE and V5) are not included in the range of any of these transition dates, suggesting that none of these three transition dates are suitable for identifying these initial growth stages. In contrast,  
Figure 4: Comparation between ground-observation of winter wheat growth stages from 2018 to 2022 and transition dates estimated by the phenological identification framework (spline model) with MODIS EVI. Each dot on the graph corresponds to observations from a different year. The distribution of transition dates derived through various methods—threshold-based (TR), derivative-based (DB), curvature-based (CU), and Gu-based (GU)—is visualized using distinct colors in panels (**a–d**). Figure 3: Comparation between ground observation of maize growth stages from 2018 to 2022 and transition dates estimated by the phenological identification framework (spline model) with TROPOMI SIF. Each dot on the graph corresponds to observations from a different year. The distribution of transition dates derived through various methods—threshold-based (TR), derivative-based (DB), curvature-based (CU), and Gu-based (GU)—is visualized using distinct colors in panels (**a–d**). the JT and T&S stages are entirely encompassed within the value range of SOS and POS, respectively, indicating that the SOS of the TR method may accurately correspond to JT, and the POS of the TR method could be used to accurately identify T&S. For the MK, MT and HV stages, which are more commonly distributed around the time span of EOS, suggesting that the EOS of the TR method may not correspond accurately to any of these three crop stages. Nevertheless, EOS remains the most suitable transition for estimating MK, MT and HV among the SOS, POS and EOS of the TR method, as these three growth stages are closest to its time span. Notably, the milk (MK) stage in 2022 occurred much earlier than in other years, possibly due to waterlogging in that particular year. The transition dates extracted by various phenological characterization methods may exhibit differences in precision and variation, as depicted in Figure 3a. In Figure 4a, the transition dates of the TR method, Figure 4b for DB method and Figures 3d and 4d for the GU method demonstrate good precisions, with distinct and narrow time spans. However, the estimations from the DB method in Figure 3b and CU method in Figures 3c and 4c exhibit some overlapping sets of transition dates. For instance, in Figure 3b, POS and SOS of DB method overlap to the extent that they nearly exclude the JT stage from the SOS range and include the T&S stage in the POS range.