基于TRMM卫星资料分析三峡蓄水前后的局地降水变化

为揭示三峡蓄水对局地气候的影响，利用TRMM 3B42卫星降水产品分析了三峡蓄水前后（以2003年为分界）库区的局地降水变化。分析表明，蓄水以后，库区西北部年累积降水量增加，东南部年累积降水量减少，这种降水变化是大尺度上降水变化的区域体现。蓄水对干流附近降水产生了一定影响，干流站点间降水量差别增大，但整个大库区平均的年累积降水量无明显变化。蓄水之后的降水变化具有季节差异。冬季几乎整个库区的降水量都有所增加；春季降水量在干流的上游个别地区和下游减少，中游增加；夏季除库区下游部分地区外，大部分库区降水量有所减少；秋季，库区的上游和中游降水增加，下游降水减少。区域平均的季节降水量无明显年际趋势。结果表明，三峡蓄水带来的降水变化空间尺度只局限在近库区，对整个大库区降水变化的影响可忽略不计

LOCAL PRECIPITATION CHANGES INDUCED BY THE THREE GORGES RESERVOIR BASED ON TRMM OBSERVATIONS

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