## 3 Results
### Comparison with GPP and VI  
The scatter plots for January 2019 in Figure 3, showing the relationship between the two SIF products and GPP and EVI at a 0.1\({}^{\circ}\) spatial resolution, highlight the differences between our retrieval results and the Caltech SIF product at high spatiotemporal resolutions. For higher goodness-of-fit (GOF) with VI, no normalization for illumination conditions was applied to the SIF products. The scatter plots revealed that our retrieval results had a slightly higher degree of dispersion, primarily due to the inclusion of the O\({}_{2}\) absorption band. Additionally, our retrieval results were more sensitive to variations in GPP and VI, leading to a significant advantage in GOF and higher intensity levels. Since high-vegetation areas typically correspond to stronger illumination, there should be a non-linear relationship between the SIF signal and VI. This non-linearity was evident in our retrieval results, while the scatter plot for Caltech SIF product and VI showed minimal slope differences between high- and low-vegetation areas. To verify the stability of the GOF differences between the two SIF products at high spatiotemporal resolution, we conducted a linear fit of two SIF products with GPP and EVI at a 0.1\({}^{\circ}\) spatial resolution on a monthly scale from January 2018 to June 2020, and calculated the GOF. The GOF calculation results are presented in Figure 4 in the form of a line chart. Due to insufficient retrievals in December 2018, the fitting results for that month showed significant bias. Both SIF products exhibited similar temporal variation in their GOF with EVI and GPP. During the southern hemisphere summer, the global SIF intensity and its gradient were higher, resulting in a better fit. Since changes in EVI accumulate over time, the variation in the goodness-of-fit between the SIF products and EVI lagged behind and was smaller compared to GPP. Notably, during the southern hemisphere summer, the improvement and enhancement ratios of the fit between our retrieval results and both EVI and GPP were higher compared to the Caltech SIF products, indicating enhanced sensitivity of the data-driven method in our study. We also present the Pearson correlation coefficients (\(p\)-values) of the two SIF products with GPP and VI at high spatiotemporal resolutions in Figure 5. The temporal trend of the \(p\)-values closely resembles that of GPP, indicating that our retrieval results consistently show a higher linear correlation with GPP and VI at high spatiotemporal resolutions. Compared to GOF, the differences in \(p\)-values between the two SIF products are smaller. Figure 6 presents the annual-scale scatter plots of the two SIF products with GPP and EVI. When comparing with VI, SIF products were normalized for illumination conditions using the solar zenith angle to balance the significant differences in illumination across various months and regions. As the spatiotemporal resolution decreased, random noise in the composite SIF products was more effectively suppressed, leading to an improvement in goodness-of-fit and a reduction in the difference between the two SIF products' fit. Figure 4: Goodness-of-fit (GOF) of the two SIF products with GPP and EVI at 0.1\({}^{\circ}\) spatial resolution and monthly scale from January 2018 to June 2020. The shaded part corresponds to December 2018 when SIF retrieves too few results. Figure 3: Scatter plot and goodness-of-fit (R\({}^{2}\)), Pearson correlation coefficient (P) of monthly SIF products with GPP and VI for January 2019 at 0.1\({}^{\circ}\) spatial resolution. Figure 7 shows the scatter plots and fitting results of the two SIF products with GPP and VI at the annual scale and 2\({}^{\circ}\) spatial resolution. At a 2\({}^{\circ}\) spatial resolution, the goodness-of-fit of the SIF products further improved. Our retrieval results maintained a noticeable advantage over the Caltech SIF product in terms of fit with GPP but showed lower fit levels with VI.