Abstract:

The increased water body caused by the Three Gorges Reservoir might bring substantial influences on the local climate and the background of largescale climate change, especially on the frequency and characteristics of meteorological disasters. How to distinguish the natural and the humaninduced climate changes is a hot common concern and a study focus of the current water science and the meteorology. In order to reveal the impact of the Three Gorges Reservoir on the local climate, the TRMM 3B42 satellite precipitation dataset was analyzed before and after 2003 (The Three Gorges Reservoir Project). The results showed that, the accumulated annual precipitation was enhanced over the northwestern parts and reduced over the southeastern area of the Three Gorges after the impoundment, which reflects the largescale precipitation changes. The cumulative annual precipitation amount changes in TRMM 3B42 and the raingauged data were in good coherence and the spatial correlation coefficient was 072(p< 001). The Three Gorges Reservoir produced a minor influence on the precipitation over the regions near the dam, and the differences among the trunk stream sites were increasing as time, but no significant changes were observed for the area mean yearly rainfall amount in both TRMM 3B42 and the raingauged observations. The precipitation change after building the reservoir exhibited seasonal differences. The rainfall increased over almost the whole region in winter. In spring, the precipitation was enhanced over parts of the upstream and most parts of the downstream, while was reduced over the midstream. Precipitation increased over most of the reservoir regions except for some downstream regions in summer. In autumn, precipitation increased in the upstream and the midstream and decreased in the downstream. The regional averaged seasonal rainfall had no significant interannual trends. Overall, the analysis implies that the impacts of the Three Gorges Reservoir on the local precipitation change are only confined in the near dam area, and the impacts on the entire large Three Gorges Region is nearly negligible. The current data length of TRMM 3B42 can only reflect the precipitation changes before and after the Three Gorges Reservoir was built. Answers to whether these variations are induced directly by the reservoir will need combined verifications of longer observations with numerical simulations