## 3 Results
### Driving Analysis of Temporal and Spatial Variation of ET in the YRB  
From Section 3.2, it was clear that each climatic factor had different effects on ET variation, but such effects were not singular but interactive and had a joint influence, and the relationships among them were complex [48]. Therefore, it was important to analyze the common influence of these driving factors on ET and to identify the dominant climatic factors on ET changes. As shown in Figure 16, it could be seen that the driving mechanisms of climatic factors affecting ET had strong spatial differences at the annual scale, and the area proportion of the dominant factors affecting ET in the study area was SR (35.16%) > SH (34.51%) > P (16.84%) > T (7.96%) > U (5.52%). In terms of spatial distribution, SR and SH occupied the largest area as the dominant factors, and they were distributed in the upper, middle, and lower reaches of the YRB. The regions where precipitation was the dominant factor of ET variation were distributed near the rivers. However, the regions where T and U were the dominant factors of ET variation covered a smaller area, mainly distributed in the middle and upper reaches of the YRB and scattered in the lower reaches of the YRB. Figure 14: Spatial distribution map (**a**) and significance test results (**b**) of correlation coefficient between U and ET at the annual scale in the YRB. A\(-\)M represent 13 sub-basins of the YRB, which are as follows: the Jinsha River Basin; the mountainous areas in the upper reaches of Dadu River and Jialing River; the confluence area of Sichuan Basin; the main stream area in the upper\(-\)middle reaches of the Yangtze River; the Wujiang River Basin; the middle reaches of the Yangtze River; the confluence area of Nanyang Basin; the Jianghan\(-\)Dongting Lake Plain; the Dongting Lake Basin; the mountainous area of Ganjiang River Basin; the Poyang Lake Plain; the confluence area of Chao Lake and the plain along Wanjiang River; and the confluence area of the Yangtze River Delta. Figure 15: Correlation significance test results of monthly U and ET in the YRB. A\(-\)M represent 13 sub-basins of the YRB, which are as follows: the Jinsha River Basin; the mountainous areas in the upper reaches of Dadu River and Jialing River; the confluence area of Sichuan Basin; the main stream area in the upper\(-\)middle reaches of the Yangtze River; the Wujang River Basin; the middle reaches of the Yangtze River; the confluence area of Nanyang Basin; the Jianghan\(-\)Dongting Lake Plain; the Dongting Lake Basin; the mountainous area of Ganjiang River Basin; the Poyang Lake Plain; the confluence area of Chao Lake and the plain along Wanjiang River; and the confluence area of the Yangtze River Delta. Combined with the area proportion (Figure 17) and spatial distribution (Figure 18) of the dominant climatic factors of monthly ET in the YRB, we found that the spatiotemporal heterogeneity of ET affected by climatic factors in 12 months in the YRB was significantly different from that at the annual scale. The annual ET variation in the YRB was mainly driven by SR and SH, and only 7.96% of the ET variation in the region was mainly driven by T. However, the climatic factor\(-\)driven partition showed that monthly ET in most regions was mainly driven by SR or T, especially in summer and autumn. The regions where ET was mainly driven by SR and T were mostly distributed in the middle and lower reaches of the YRB, and they were only distributed in the headquarters of the YRB in individual months. Combined with Figures 7 and 11, it could be seen that SR and T were significantly positively correlated with ET in the middle and lower reaches of the YRB, while they were significantly negatively correlated with ET in the headwaters of the YRB. In addition, the highest proportion of SR\(-\)driven area occurred in August, about 60%, and the lowest occurred in November, about 15%. The highest proportion of the T\(-\)driven area occurred in September, about 51%, and the lowest occurred in December, about 9%.