## 3 Results
### Trends of Climate Factors and Vegetation  
3.3.1. Trends in Climate Factors  
Figures 5 and A1 show the spatial distributions of trends and trend significance for five climatic factors over China, as well as statistical trends in sub-regions, from 1999 to 2018. Precipitation shows an upward trend of 3.18 mm yr\({}^{-1}\) over China (Figure 5a). The most significant trends (>5 mm yr\({}^{-1}\)) are distributed in the eastern parts of China (Figure 5b), and 12.76% of regions (primarily in Northeastern and Central-Western China) undergo significant (\(p\) < 0.05) increases (Figure A1a). Among the four sub-regions, TMon and TP have the most and least intense trends, with values of 4.97 mm yr\({}^{-1}\) and 0.30 mm yr\({}^{-1}\), respectively (Figure 5a).  
Mainland China shows a warming mean temperature trend of 0.020 \({}^{\circ}\)C yr\({}^{-1}\) (Figure 5c,d). Spatially, 24.43% of the regions (primarily in Southwestern, Northern, and Southeastern China) experienced significant (\(p\) < 0.05) increases (Figure A1b). Among the four sub-regions, TP and TCon show the most (0.023 \({}^{\circ}\)C yr\({}^{-1}\)) and least (0.012 \({}^{\circ}\)C yr\({}^{-1}\)) significant trends (Figure 5d).  
The overall trend in wind speed over Mainland China from 1999 to 2018 is 0.010 m s\({}^{-1}\) (Figure 5e). More than 73% of China experienced increasing wind speeds, and 38.798% of regions (primarily in Southwestern and Southeastern China) show significant (\(p\) < 0.05) increases (Figures 5f and A1c). Among the four sub-regions, SubT and TMon show the most (0.014 m s\({}^{-1}\)) and least (0.004 m s\({}^{-1}\)) significant trends (Figure 5e).  
Figure 4: Trends of annual ET and GPP between 1999 and 2018: (**a**,**d**) spatial distribution of annual ET and GPP trend over Mainland China; (**b**,**e**) spatial distribution of annual ET and GPP trend significance over Mainland China; (**c**,**f**) statistical trends of annual ET and GPP over China.  
Although the specific humidity over China has a slightly positive trend (1.29 \(\times\) 10\({}^{-5}\) kg kg\({}^{-1}\) yr\({}^{-1}\)), particularly in SubT (3.13 \(\times\) 10\({}^{-5}\) kg kg\({}^{-1}\) yr\({}^{-1}\)), TCon has a trend of 0 and TP has a negative trend of \(-\)0.34 \(\times\) 10\({}^{-5}\) kg kg\({}^{-1}\) yr\({}^{-1}\) (Figure 5j). Spatially, the most significant increasing trends are distributed over Southern China, and 26.50% of the areas show significant (\(p<0.05\)) increases.  
Unlike other climate factors, solar radiation decreases over the whole of China (\(-\)1.54 W m\({}^{-2}\) yr\({}^{-1}\)) from 1999 to 2018 (Figure 5i). Only TP has a slightly increasing value (0.27 W m\({}^{-2}\) yr\({}^{-1}\)); TMon, TCon, and SubT have decreasing trends of \(-\)3.89 W m\({}^{-2}\) yr\({}^{-1}\), \(-\)1.55 W m\({}^{-2}\) yr\({}^{-1}\), and \(-\)0.25 W m\({}^{-2}\) yr\({}^{-1}\), respectively (Figure 5i). Spatially, the most significant increasing trend is distributed over Southwestern China, while only 6.13% of the areas have significant (\(p<0.05\)) increases. The area with significant (\(p<0.05\)) decreasing trends accounts for 18.70%, mainly in the central and northeastern parts of the country.  
Figure 5: Trends of climate factors from 1999 to 2018 over Mainland China. Note: SH is expanded by 10\({}^{5}\) times. (**a,c,e,g,i**) includes the statistical trends in sub-regions from 1999 to 2018. (**b,d,f,h,j**) includes the spatial distributions of trends for five climatic factors over China from 1999 to 2018.