## 3 Results
### Spatial Analysis of SIF Data Accuracy Improvement before and after  
The spatial characteristics of the average values of RTSIF satellite data before improvement for each quarter (March to May are spring, etc.) are shown in Figure 10 (left column). High values of SIF data are primarily distributed in the cropland area on the northern and southern slopes of the Tianshan Mountains, as well as in the pasture grassland area of the Tianshan and Altai Mountains. Conversely, low values are predominantly found in regions with a smaller leaf area index, such as the Gurbantunggut Desert (desert vegetation area) and the eastern Gobi Desert.  
Combining land use data with two precision improvement methods, the final precision improvement results achieved by the RTSIF satellite are shown in Figure 10 (right column). The overall improvement in the mean values of the SIF data for each quarter was 0.11% (0.037% for cultivated and farmland area, 0.028% for pasture grassland area, 0.016% for desert vegetation area, and 0.025% for other area). The most significant improvement was observed in the spring and summer seasons (improvement rate of 0.071%). Specifically, in spring, as snow begins to melt, vegetation (including short-lived vegetation) begins to grow, the contribution of SIF has increased. Which is coherent with the overall enhancement of SIF attributes in the study area after improvement. In particular, significant improvements were observed in regions with a higher leaf area index, such as the northwestern part of the Altai Mountains and both slopes of the Tianshan Mountains. The attributes of the Gurbantunggut Desert also showed a synchronized enhancement, with results falling within a reasonable attribute range for arid regions [57; 58].  
In summer, most regions have completed snowmelt, and vegetation continues to grow as solar radiation increases. The contribution of the SIF further increases, which is consistent with the overall enhancement of SIF attributes in the study area after improvement. In particular, regions with higher vegetation cover, such as the Altai Mountains and both slopes of the Tianshan Mountains, experience a further increase in the enhancement rate. The attributes in desert areas and similar regions remain within a reasonable range for arid regions [59; 60; 61].  
In autumn and winter, snow begins to accumulate in most regions, and vegetation growth slows as the overall solar radiation decreases, the contribution of SIF decreases, and the overall change is not significant. This aligns with the overall lower and relatively less pronounced enhancement of the SIF attributes in the study area after improvement. The western part and both slopes of the Tianshan Mountains are areas where the enhancement of SIF attributes is more pronounced during the autumn and winter.  
Additionally, after improvement, the annual average SIF (GPP) data for various underlying surfaces in the northern region of Xinjiang was 0.13 mw/m\({}^{2}\)/nm/sr (0.26 mw/m\({}^{2}\)/nm/sr for cultivated and farmland area, 0.14 mw/m\({}^{2}\)/nm/sr for pasture grassland area, 0.034 mw/m\({}^{2}\)/nm/sr for desert vegetation area, and 0.11 mw/m\({}^{2}\)/nm/sr for other area).