| 摘要: |
| 水体中δ18O和δD在自然界中含量稀少，对环境变化极为敏感并能够记录环境变化。水稳定同位素技术被广泛应用于水文气象、气象诊断和古气候恢复等领域。根据在澳大利亚阿德莱德地区收集的前后跨4 a日降水中δD、δ18O资料，分析该地区日时间尺度下降水中δD、δ18O和氘盈余（d）的变化特征以及与各气象要素的关系，为理解云下二次蒸发与气象要素间的联系，探讨区域水循环机理提供依据。结果表明：在研究区，日时间尺度下大气降水中δ18O与降水量、相对湿度在全年和冬夏半年均表现出显著负相关关系，与温度在全年以及冬半年表现出显著正相关关系，在夏半年表现出不显著的正相关关系，表明该地区降水中氧同位素的变化具有显著的降水量效应和湿度效应。冬半年降水中d值明显高于夏半年，指示冬夏半年间的降水气象条件与水汽来源存在较大差异。阿德莱德地区的大气降水线为：δD=6.38×δ18O+6.68，斜率和截距明显小于全球大气水线GMWL，表征出阿德莱德地区较为干旱的气候特征。在降水量、相对湿度偏低以及气温值偏高的降水事件中，大气水线出现显著偏低的斜率和截距，表明雨滴在下落过程中受到强烈的二次蒸发影响。研究结果将为澳大利亚阿德莱德地区水文气象、气象诊断和古气候恢复等领域提供基础。 |
| 关键词: 阿德莱德 大气降水 稳定同位素 大气降水线 逐步回归分析 |
| DOI：10.7515/JEE222045 |
| CSTR： |
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| 基金项目:国家自然科学基金项目（41772373，42001080） |
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| Variation characteristics of stable isotopes in atmospheric precipitation in Adelaide, Australia |
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WANG Dizhou, ZHANG Xinping, LIU Zhongli, LI Guang, GUAN Huade
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1. School of Geographic Sciences, Hunan Normal University, Changsha 410081, China
2. Hunan Key Laboratory of Geospatial Big Data Mining and Application, Hunan Normal University, Changsha 410081, China
3. School of the Environment, Flinders University, Adelaide 5001, Australia
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| Abstract: |
| Background, aim, and scope Stable isotope in water could respond sensitively to the variation of environment and be reserved in different geological archives, although they are scarce in the environment. And the methods derived from the stable isotope composition of water have been widely applied in researches on hydrometeorology, weather diagnosis, and paleoclimate reconstruction, which help well for understanding the water-cycle processes in one region. Here, it is aimed to explore the temporal changes of stable isotopes in precipitation from Adelaide, Australia and determine the influencing factors at different timescales. Materials and methods Based on the isotopic data of daily precipitation over four years collected in Adelaide, Australia, the variation characteristics of daily δD, δ18O, and dexcess in precipitation and its relationship with meteorological elements were analyzed. Results The results demonstrated the local meteoric water line (LMWL) in Adelaide, was δD=6.38×δ18O+6.68, with a gradient less than 8. There is a significant negative correlation between daily δ18O and precipitation amount or relative humidity at daily timescales in both the whole year and wither/summer-half year (p＜0.001), but a significant positive correlation between daily δ18O and temperature in the whole year and the winter half-year (p＜0.001). Discussion The correlation coefficients between δ18O and daily mean temperature didn’t show a significant positive correlation, which may be attributed to that the precipitation in Adelaide area in January was mainly influenced by strong convective weather, and the stable isotope values in precipitation were significantly negative. Furthermore, this propose was also evidenced by the results from dexcess of precipitation with larger value in the winter half-year than that in the summer half-year, which may be resulted from the precipitation events in winter are mostly influenced by oceanic water vapor, while the sources of water vapor in summer precipitation events are more complicated and influenced by strong convective weather. On the other hand, the slope and intercept of the δ18O—P regression lines in the summer months (−0.41 and 0.50‰) are larger and smaller than those in the winter months (−0.22 and −2.15‰), respectively, indicating that the precipitation stable isotopes have a relatively stronger rainout effect in the summer months than in the winter months. Besides, the measured values of δ18O in daily precipitation have a good linear relationship with our simulated values of δ18O, demonstrating the established regression model could provide a reliable simulation for the δ18O values in daily precipitation in Adelaide area. It’s worth noting that the precipitation events with low precipitation amount, low relative humidity and high temperature, usually had relatively small slope and intercept of MWL, implying that raindrops may be strongly affected by sub-cloud secondary evaporation in the falling process. Conclusions The variation of δ18O in daily precipitation from Adelaide region was controlled by different factors at different timescales. And the water vapor sources and the meteorological conditions of precipitation events (such as the degree of sub-cloud secondary evaporation) also played an important role on the variation of δ18O. Recommendations and perspectives Stable isotope in daily precipitation can provide more accurate information about water-cycle and atmosphere circulation, it is therefore necessary to continue to collect and analyze daily-scale precipitation data over a longer time span. The results of this study will provide the basis for the fields of hydrometeorology, meteorological diagnosis and paleoclimate reconstruction in Adelaide, Australia. |
| Key words: Adelaide precipitation stable isotopes meteoric water line stepwise regression analysis |
