基于水汽解析的黄河源区极端降水机理研究

Study on the Mechanism of Extreme Precipitation in the Source Area of the Yellow River Based on Water Vapor Analysis

黄河源区位处于青藏东北部,是中国夏季水汽输送转运站与重大灾害水汽输送的关键区之一,研究黄河源区极端降水水汽输送机理,对理解黄河源区、黄河源区气候、水文过程具有重要的意义。本文利用拉格朗日混合单粒子轨道模型(HYSPLIT4)对2015~2017年7~8月的黄河源区极端降水事件的水汽输送情况进行了定量的分析,探讨了黄河源地区水汽输送特征以及极端降水事件的异常水汽输送的差异,并评估了各水汽源地对黄河源区流域内极端降水的贡献值。结果表明:黄河源区6~9月的极端降水事件占极端降水事件总数的90.4%。黄河源地区极端降水北部与东部的水汽通道主要来源于欧亚大陆西部的贝加尔湖地区,西部的水汽通道主要来源于黄河源周边地区,南部的水汽通道主要来源于中国南海–孟加拉湾以及印度洋,太平洋的水汽对黄河源区域的影响很小。由定量分析的结果可获得以下结论:2015~2017年黄河源区极端降水水汽通道主要来源于欧亚大陆西部的贝尔加湖地区与黄河源及周边地区,两者贡献值合计大于66%,远超其余区域对黄河源极端降水的影响,是黄河源极端降水的重要水汽来源;欧亚大陆西部极端水汽数量贡献值为43%,比黄河源区高18%,但欧亚大陆的空气较为干燥,水汽团水汽含量较低,比湿贡献值为34%,与黄河源贡献值32%相近。

The source area of the Yellow River is located in the northeast of Qinghai-Tibet Plateau, which is one of the key areas of water vapor transportation transfer station and major disaster water vapor transportation in summer in China. Studying the mechanism of extreme precipitation water vapor transportation in the source area of the Yellow River is of great significance to understanding the climate and hydrological process of the source area of the Yellow River. In this paper, quantitative analysis was made about the water vapor transportation of extreme precipitation events in the source area of the Yellow River from July to August in 2015, 2016 and 2017 by the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT4);discussion was made about the characteristics of water vapor transportation in the source area of the Yellow River and the differences of abnormal water vapor transportation of extreme precipitation events, and evaluation was made about the contribution for the extreme precipitation in the basin of the source area of the Yellow River from each water vapor source. The results showed that the extreme precipitation events from June to September in the source area of the Yellow River account for 90.4% of the total extreme precipitation events. The water vapor channels in the north and east extreme precipitation in the source area of the Yellow River mainly come from the Lake Baikal area in the west of Eurasian Continent;the water vapor channels in the west mainly come from the surrounding areas of the source area of the Yellow River, and the water vapor channels in the south mainly come from the South China Sea-Bay of Bengal and the Indian Ocean, but the water vapor from the Pacific has little impact on the source area of the Yellow River. The following conclusions can be obtained from the results of quantitative analysis: the extreme precipitation water vapor channels in the source area of the Yellow River from 2015 to 2017 mainly come from the Lake Baikal area in the west of Eurasian Continent, the source area of the Yellow River and its surrounding areas. The total contribution value of the two is more than 66%, far more than the impact of other areas on the extreme precipitation in the source area of the Yellow River. So they are the important water vapor source of extreme precipitation in the source area of the Yellow River;the contribution value of extreme water vapor in western Eurasian Continent is 43%, which is 18% higher than that in the source area of the Yellow River. However, the air in Eurasian Continent is relatively drier, and the moisture of water vapor mass is low, and the contribution value of specific humidity is 34%, which is close to 32% of the contribution value of the source area of the Yellow River.