## 3 Results
### Global SIF Product: Annual Average, Maximum Magnitude, and Trend of SIF  
The magnitude and spatial pattern of the annual mean SIF averaged over the period from 2001 to 2017 are illustrated in Figure 9. The annual mean SIF showed the highest values in the tropical regions, intermediate values in the eastern United States, southern China, and central Europe, and the lowest values in the barren regions. This was largely dependent on climate conditions (air temperature, precipitation, and solar radiation) and vegetation type.  
Figure 8: Relationship between 8-day SIF from our GOSIF product and 8-day GPP from the FLUXNET 2015 Tier 1 dataset. The 8-day flux tower-based GPP was temporally aggregated from the daily values.  
We also compared annual mean and maximum daily values between GOSIF and MODIS GPP in 2015 (Figure 10). The spatial pattern of annual mean SIF (Figure 10a) was generally in accordance with the spatial pattern of annual mean GPP based on the MODIS GPP product (Figure 10c). The highest value of maximum daily SIF was observed in the U.S. Corn Belt region, followed by central Europe, northeastern China, Argentina, and the tropical regions (Figure 10b). In contrast, maximum daily MODIS GPP had the prominently highest values in the tropical regions, followed by the U.S. Corn Belt region (Figure 10d). We also compared GOSIF with the 1\({}^{\circ}\) OCO-2 SIF that was directly aggregated from the discrete SIF soundings, and found that our new SIF (Figure 10a,b) well-captured the spatial variations in both annual mean and maximum daily SIF presented in the coarse-resolution SIF (Figure 10e,f). Compared with the coarse-resolution SIF that was directly aggregated from OCO-2 soundings and had large data gaps, GOSIF had finer spatial resolution, globally continuous coverage, and a much longer record, and is better suited for studying ecosystem function and carbon cycles at various spatial and temporal scales.  
Figure 9: Magnitude and spatial patterns of the annual mean SIF of our GOSIF product (0.05\({}^{\circ}\), 8-day) over the period from 2001 to 2017. The units are W m\({}^{-2}\)\(\mu\)m\({}^{-1}\) sr\({}^{-1}\).  
During the period from 2001 to 2017, more than half of the land grid cells showed no significant trend in SIF (\(p>0.05\), Figure 11a). For the remaining grid cells, SIF increased over most regions (e.g., India, most of China), and negative trends were only detected in a few regions (e.g., eastern Brazil). The annual global mean SIF had a significant positive trend (0.0004 W m\({}^{-2}\)\(\upmu\)m\({}^{-1}\) sr\({}^{-1}\) per year, \(p<0.001\)) during the past 17 years (Figure 11b). The global mean EVI showed a similar positive trend (0.0006 yr\({}^{-1}\), \(p<0.001\)) during the 17-year period, while no significant trend was found in MODIS GPP (\(p>0.1\)) over 2001 to 2015. For the period that MODIS GPP was available (2001-2015), SIF still exhibited a significant positive trend, with a slope (0.0003 W m\({}^{-2}\)\(\upmu\)m\({}^{-1}\) sr\({}^{-1}\) per year) slightly smaller than that of 2001-2017, and EVI also had a significant positive trend, with a slope (0.0006 yr\({}^{-1}\)) identical with that of 2001-2017.  
Figure 10: Annual mean and maximum SIF of our GOSIF product (0.05\({}^{\circ}\), 8-day) and comparison with annual/maximum GPP of the Moderate Resolution Imaging Spectroradiometer (MODIS) GPP product and the annual mean/maximum SIF of the 1\({}^{\circ}\) OCO-2 SIF directly aggregated from discrete OCO-2 SIF soundings in 2015: (**a**) Annual mean new 0.05\({}^{\circ}\) SIF, (**b**) maximum daily new 0.05\({}^{\circ}\) SIF, (**c**) annual MODIS GPP, (**d**) maximum daily MODIS GPP, (**e**) annual mean 1\({}^{\circ}\) SIF, and (**f**) maximum daily 1\({}^{\circ}\) SIF.