Modelling the isotopic composition of snow using backward trajectories: a particular precipitation event in Dronning Maud Land, Antarctica
Modelling the isotopic composition of snow using backward trajectories: a particular precipitation event in Dronning Maud Land, Antarctica
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使用向后轨迹模拟雪的同位素组成：南极洲 Dronning Maud 地的一次特殊降水事件
DOI：
10.3189/172756404781814230
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发表时间：
2004
影响因子：
2.9
通讯作者：
M. P. Scheele
中科院分区：
文献类型：
--
作者：
M. Helsen;R. V. D. van de Wal;M. R. van den Broeke;E. Kerstel;V. Masson‐Delmotte;H. Meijer;C. Reijmer;M. P. Scheele
摘要 我们考虑了 2002 年 1 月在南极洲 Dronning Maud 地西部发生的一次具体积累事件。积雪几天后获得雪样。我们结合气象分析和同位素建模来描述运输过程中水分的同位素组成。根据欧洲中期天气预报中心的业务档案数据计算了向后轨迹，以便可以重建气团将水蒸气输送到积聚地点的历史。该轨迹研究表明，大部分输送路径上的气团并未（超）饱和，这与拉格朗日分馏模型中的假设相反，并且对于南极洲的大多数降水事件来说可能都是如此。沿着轨迹模拟的分馏太有限，无法解释测量到的雪的同位素含量。结果表明，观测到的降水同位素组成是由最初更贫化的水的分馏产生的。水蒸气的初始同位素组成较低可能是由于大气与沿轨迹的更多贫化空气混合或由于早期的冷凝循环而导致的，而不是由轨迹捕获的。这与大气环流模型产生的同位素场一致，表明从赤道到南极洲的同位素组成存在梯度。
Abstract We consider a specific accumulation event that occurred in January 2002 in western Dronning Maud Land, Antarctica. Snow samples were obtained a few days after accumulation. We combine meteorological analyses and isotopic modelling to describe the isotopic composition of moisture during transport. Backward trajectories were calculated, based on European Centre for Medium-Range Weather Forecasts operational archive data so that the history of the air parcels transporting water vapour to the accumulation site could be reconstructed. This trajectory study showed that the air masses were not (super)saturated along most of the transport path, which is in contrast with assumptions in Lagrangian fractionation models and probably true for most precipitation events in Antarctica. The modelled fractionation along the trajectories was too limited to explain the measured isotopic content of the snow. It is shown that the observed isotopic composition of precipitation resulted from fractionation of initially more depleted water. This lower initial isotopic composition of water vapour might result from atmospheric mixing with more depleted air along the trajectory or from earlier condensation cycles, not captured by the trajectories. This is in accordance with isotope fields resulting from general circulation models, indicating a gradient in isotopic composition from the Equator to Antarctica.