| 引用本文: | 薛如，庞洪喜，詹兆君，王佳佳，许涛，顾小琴.2023.典型梅雨持续性降水事件的水汽同位素特征及其成因[J].地球环境学报,14(4):434-443 |
| XUE Ru, PANG Hongxi, ZHAN Zhaojun, WANG Jiajia, XU Tao, GU Xiaoqin.2023.Water vapor isotope characteristics and causes of a typical long-term precipitation event during Meiyu period[J].Journal of Earth Environment,14(4):434-443 |
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| 摘要: |
| 梅雨期持续性强降水是江淮地区重要的灾害天气，往往给降水地区带来巨大的生命与经济损失。2016年7月1—7日，南京地区经历了一场历时7 d的典型梅雨降雨过程，本文针对此次降水事件的大气水汽稳定同位素变化特征及其成因进行相关研究。研究发现：水汽稳定同位素的变化特征与大尺度有组织对流活动和大气环流有良好的对应关系。水汽稳定同位素随时间分别呈现δ18O的“U型”演化和过量氘的波动变化，二者在不同降雨阶段的演化特征可以指示产生降雨的天气系统的移动与切换，其中水汽过量氘随时间变化的极大值和极小值转折点分别反映了低涡系统开始与结束影响研究区、冷切变线消散、槽线过境以及台风外围水汽抵达研究区的时间。结果表明：多个天气系统连续作用于研究区及其带来的不同水汽源的持续供给，是此次梅雨期降水持续维持的重要条件。 |
| 关键词: 梅雨 持续性降雨 水汽稳定同位素 天气系统 水汽来源 |
| DOI：10.7515/JEE222062 |
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| 基金项目:国家自然科学基金项目（41771031） |
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| Water vapor isotope characteristics and causes of a typical long-term precipitation event during Meiyu period |
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XUE Ru, PANG Hongxi, ZHAN Zhaojun, WANG Jiajia, XU Tao, GU Xiaoqin
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School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China
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| Abstract: |
| Background, aim, and scope Long-term rainstorm during Meiyu period is an important disaster weather in the area of the middle and lower reaches of the Yangtze River, often bringing huge loss of life and property. Since Jul. 1st, 2016, the Jianghuai region has experienced a continuous rainfall process lasting for seven days. In order to understand variation characteristics and causes of water vapor isotopes during Meiyu period, we conducted continuous monitoring of stable isotopes of water vapor during the rainfall period at the station for observing regional processes of the earth system in Nanjing University. Materials and methods We collected and analyzed the water vapor isotopes in the near-surface atmosphere using wavelength scanned cavity ring-down spectrometer (WS-CRDS) and use a set of accurate and reliable atmospheric water vapor stable isotope calibration methods to calibrate various deviations during the process of instrument observation. Results It is found that the variation characteristics of water vapor isotopes have a good correspondence with large-scale organized convective activity and atmospheric circulation. The variation of water vapor δ18O show U-shaped characteristics while d excess show a fluctuation characteristic over time. Discussion The evolution characteristics of δ18O and d excess in different rainfall stages can indicate the movement and switching of the synoptic system. In stage 1, the δ18O value of water vapor rapidly depleted, and the d excess value of water vapor increased first and then decreased showing an inverted “V” shape, corresponding to the water vapor source switching from the warm and humid oceanic air mass at the front of the southwest vortex to the dry and cold air mass from the inland after the southwest vortex transit during rainfall. In stage 2, the rainfall decreases, and the water vapor δ18O value remains in a relatively depleted state on the basis of stage 1; the water vapor d excess value shows a fluctuating change of rising-falling-rising, corresponding to the invasion and retreat of dry and cold air masses during the shear line rainfall. In stage 3, rainfall intensified again, but contrary to the first stage, water vapor δ18O was enriched during the rainfall, while water vapor d excess as a whole showed a fluctuating downward trend, echoing the enhanced southern water vapor delivered at this stage. In stage 4, the typhoon gradually approached the coast of the South China Sea, bringing a large amount of oceanic water vapor from the south, so that the water vapor δ18O was further enriched on the basis of stage 3, and the water vapor d excess reduced. Therefore, the turning points of water vapor d excess reflect the times of vortex system starting affecting the study area, the dissipation of cold shear lines, the transit of trough lines and the arrival of typhoon water vapor. Conclusions Thus, continues action of different synoptic systems and multiple moisture sources supplying are important conditions for the long-term maintenance of precipitation during Meiyu period. Recommendations and perspectives Due to the different causes of rainfall events, the characteristics of water vapor isotope may be different. By analyzing the water vapor isotope characteristics of more rainfall events of different causes, we can further clarify the relationship between water vapor isotope characteristics and different weather systems during Meiyu period. |
| Key words: Meiyu long-term precipitation water vapor isotope synoptic system moisture source |
