## 3 Results
### The Spatiotemporal Characteristics of the Impact of Environmental Factors on GPP  
#### 3.3.1 The Impact of Environmental Factors on GPP in Different Weather Conditions  
Based on the weather condition classification results in Table 4, we conducted a correlation analysis between the station data and satellite data corresponding to different weather conditions to clarify the impact of environmental factors on GPP under these conditions. GPP in arid regions exhibits a strong positive correlation with PAR, VPD, SWC, Tair, and Tsoil across different surfaces and weather conditions (Figure 8). Among them, under sunny, cloudy, and overcast conditions in grassland areas, the correlation coefficient between GPP and PAR is the highest, followed by Tsoil, Tair, and VPD, with SWC being the lowest. This indicates that the carbon sequestration capacity increases with the increase in PAR. In desert vegetation areas, the ranking of correlation coefficients between GPP and environmental factors under sunny conditions is consistent with that in grassland areas, with PAR still being the dominant influencing factor on GPP, while SWC has the least influence. However, under cloudy conditions, VPD is the dominant influencing factor on GPP, while PAR ranks second. Under overcast conditions, Tair is the dominant influencing factor on GPP, followed by Tsoil and PAR. In farmland areas, the correlation coefficients between GPP and PAR, VPD, Tair, and Tsoil show no significant differences under sunny, cloudy, and overcast conditions. These four factors jointly dominate the carbon sequestration capacity of cultivated farmland areas. However, although SWC still has the lowest correlation, this value is significantly higher under cloudy conditions than that of the other two surfaces. Therefore, in grassland areas, PAR is the dominant influencing factor on GPP under all weather conditions. In desert vegetation areas, PAR is the dominant influencing factor on GPP under sunny conditions, VPD is the dominant influencing factor under cloudy conditions, and Tair is the dominant influencing factor under overcast conditions. In farmland areas, PAR, VPD, Tair, and Tsoil jointly dominate GPP under the three different weather conditions.  
Figure 8: The correlation between GPP and five environmental factors (PAR, VPD, SWC, Tair, and Tsoil) under different weather conditions and underlying surfaces (** indicates passing the significance test of 0.05).  
Additionally, under sunny conditions, the degree of the mutual response between GPP and different environmental factors is most significant in grassland areas, followed by farmland areas and desert vegetation areas. Under cloudy conditions, the degree of interaction between GPP and different environmental factors is also most significant in grassland areas, but desert vegetation areas rank second, while cultivated land and pasture areas rank last. Under overcast conditions, the degree of mutual response between GPP and different environmental factors is most significant in farmland areas, followed by grassland areas and desert vegetation areas. Therefore, GPP in desert vegetation areas is most affected by weather conditions, followed by farmland areas, and is least affected in grassland areas.