## 3 Results
### Spatial Patterns of Estimated GPP
The differences between GPP\({}_{\rm SIF}\) and those of the other products are shown in Figure 5. During DJF, the differences between GPP\({}_{\rm SIF}\) and GPP\({}_{\rm MODIS}\) were mainly between -100 and 200 g C\(\cdot\)m\({}^{-2}\), with differences ranged between 0 and 100 g C\(\cdot\)m\({}^{-2}\) in Europe and Asia, ranged between -100 and 0 g C\(\cdot\)m\({}^{-2}\) in Southern Asia and Southeast Asia, ranged between 100 and 200 g C\(\cdot\)m\({}^{-2}\) in Central Africa and the Amazon. The differences between the GPP\({}_{\rm SIF}\) and GPP\({}_{\rm GLASS}\) were mainly between -100 and 100 g C\(\cdot\)m\({}^{-2}\). In tropical regions such as Southeast Asia, Central Africa, and the Amazon, the differences were mainly between -100 and 0 g C\(\cdot\)m\({}^{-2}\), in HAM, the differences between GPP\({}_{\rm SIF}\) and GPP\({}_{\rm MODIS}\) were mainly between 0 and 100 g C\(\cdot\)m\({}^{-2}\), with a few regions in the Amazon, Central Africa, and Europe having differences ranged between 100 and 200 g C\(\cdot\)m\({}^{-2}\); in the northern part of Australia, it reached -100 g C\(\cdot\)m\({}^{-2}\). The differences between GPP\({}_{\rm SIF}\) and GPP\({}_{\rm GLASS}\) were mainly between 0 and 100 g C\(\cdot\)m\({}^{-2}\), with some parts of the Amazon, Central Africa, and Europe exhibiting differences around -100 g C\(\cdot\)m\({}^{-2}\). In JJA, the differences between GPP\({}_{\rm SIF}\) and GPP\({}_{\rm MODIS}\) were mainly between -100 and 200 g C\(\cdot\)m\({}^{-2}\), with differences between 100 and 200 g C\(\cdot\)m\({}^{-2}\) in the equatorial tropics. Some regions in Central Africa exhibited differences as high as 200 to 300 g C\(\cdot\)m\({}^{-2}\). The differences between GPP\({}_{\rm SIF}\) and GPP\({}_{\rm GLASS}\) were mainly between -100 and 200 g C\(\cdot\)m\({}^{-2}\); Eastern Europe and North Asia exhibited differences in the range of 100 to 200 g C\(\cdot\)m\({}^{-2}\), with one part of the central Amazon reaching a difference of 200 g C\(\cdot\)m\({}^{-2}\). In SON, the difference between GPP\({}_{\rm SIF}\) and GPP\({}_{\rm MODIS}\) was mainly in the range of -100 to 200 g C\(\cdot\)m\({}^{-2}\). The larger differences were mostly located near the equator. The differences between the GPP\({}_{\rm SIF}\) and GPP\({}_{\rm GLASS}\)  
Figure 4: Global GPP for all vegetation coverage types in GPP\({}_{\rm SIF}\), GPP\({}_{\rm MODIS}\) and GPP\({}_{\rm GLASS}\) in different seasons in 2014.  
were mainly between -100 and 100 g C\(\cdot\)m\({}^{-2}\). It is noteworthy that some of the differences around the equator reached 200 g C\(\cdot\)m\({}^{-2}\), especially in the Guiana Plateau in northern South America. It is not difficult to determine that many of the large differences were concentrated in tropical regions and regions with high altitudes. In humid tropical regions at lower latitudes, where the temperature and humidity requirements for photosynthesis are adequately satisfied, the vegetation coverage types are complex and unevenly distributed, resulting in large differences in GPP and inaccurate predictions. Areas at higher latitudes or altitudes, where there are limited temperature and precipitation and so photosynthesis is limited, have homogeneous vegetation distributions and are therefore less complex than areas in the tropics. As a result, the GPP of these areas is lower overall, and the differences in GPP between various vegetation types are small. Therefore, predictions in these areas have appeared to be more accurate.