长江流域蒸发水汽去向及其对降水的贡献

Desitiny of the moisture evaporated from the Yangtze River basin and its contribution to precipitation in downwind regions

  • 摘要: 长江流域地处东亚季风的关键路径,蒸发强度大且水汽输送活跃,但蒸发水汽去向及其对下风区降水的贡献尚不明确。本文利用ERA5气象数据、CN05.1与GPCP V3.2降水融合数据、GLEAM与OAFlux蒸发融合数据驱动WAM-2layers模型,追踪1984—2022年长江全流域、上游及中下游区域蒸发水汽去向,并量化其对下风区降水的贡献。结果表明:长江流域蒸发水汽主要对流域内部、流域东北方向的亚洲大陆及周边海洋、太平洋北部产生降水贡献;长江全流域、长江上游和长江中下游的降水再循环率分别为12.18%、14.72%和5.81%;长江流域对下风向降水的影响呈现明显的季节性规律,春夏贡献量增加且影响范围扩张、秋冬贡献量减少且影响范围收缩;长江流域蒸发水汽在长江源、长江下游和东海、北太平洋西部部分地区的降水贡献呈显著增长趋势,而在传输路径和落区范围上,长江流域的降水贡献具有较高的年际稳定性。

     

    Abstract: The Yangtze River basin, situated along a pivotal East Asian monsoon pathway, is characterized by substantial evaporation and dynamic moisture transport processes. However, the destination of evaporated water vapor and its contribution to precipitation in downwind regions remain unclear. In this study, the ERA5 meteorological dataset, merged CN05.1 and GPCP V3.2 precipitation datasets, as well as merged GLEAM and OAFlux evaporation datasets, were utilized to drive the WAM-2layers model. This model was employed to track the destination of evaporated moisture from the entire Yangtze River basin, its upper reaches, and middle-lower reaches during 1984—2022, so as to quantify its contribution to precipitation in downwind regions. Results show that: ① Moisture from the Yangtze River basin mainly contributes precipitation to the basin itself, the Asian continental areas and adjacent oceanic regions to the northeast of the basin, and the northern Pacific. ② Precipitation recycling ratios for the entire basin, the upper reaches, and the middle-lower reaches are 12.18%, 14.72%, and 5.81%, respectively. ③ The impact on downwind precipitation exhibits distinct seasonal patterns: the contributions increase and the affected area expands during spring and summer, while the contributions decrease and the affected area contracts during autumn and winter. ④ The precipitation contribution shows a significant increasing trend in the Yangtze River source region, the lower reaches, the East China Sea, and parts of the western North Pacific. Regarding to transmission pathways and moisture sinks, the precipitation contribution from the Yangtze River basin demonstrates high interannual stability.

     

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