Evaluating the Roles of Rainout and Post-Condensation Processes in a Landfalling Atmospheric River with Stable Isotopes in Precipitation and Water Vapor
Evaluating the Roles of Rainout and Post-Condensation Processes in a Landfalling Atmospheric River with Stable Isotopes in Precipitation and Water Vapor
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DOI：
10.3390/atmos10020086
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发表时间：
2019-02
期刊：
影响因子：
2.9
通讯作者：
H. Mix;S. Reilly;Andrew Martin;G. Cornwell
中科院分区：
文献类型：
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作者：
H. Mix;S. Reilly;Andrew Martin;G. Cornwell
大气河流（AR）和更广泛的锋面系统往往在降水中稳定同位素的时间序列中表现出明显的“V”形。尽管这些“V”形状的规模很大且分布广泛，但关于这些变化是否是由降雨程度的变化（我们使用稳定同位素的瑞利蒸馏确定）驱动的，还是由后凝结过程（例如云下蒸发和水凝物与周围蒸汽之间的平衡同位素交换）驱动的争论仍然存在。在这里，我们展示了 2016 年 3 月 5 日至 7 日（阿肯色州）加利福尼亚州博德加湾的配对降水和水汽同位素时间序列记录。表面蒸汽的稳定同位素组成以及温度和相对湿度等独立的气象限制表明，降雨和后凝结过程在事件的不同阶段占主导地位。我们发现，瑞利蒸馏在峰值 AR 条件（峰值降雨量为 55%）期间进行控制，而后冷凝过程在事件边缘降水量减少期间具有最大影响。这些结果和分析揭示了有关 AR 事件的时间演变以及在局部尺度上控制它们的物理过程的关键问题。
Atmospheric rivers (ARs), and frontal systems more broadly, tend to exhibit prominent “V” shapes in time series of stable isotopes in precipitation. Despite the magnitude and widespread nature of these “V” shapes, debate persists as to whether these shifts are driven by changes in the degree of rainout, which we determine using the Rayleigh distillation of stable isotopes, or by post-condensation processes such as below-cloud evaporation and equilibrium isotope exchange between hydrometeors and surrounding vapor. Here, we present paired precipitation and water vapor isotope time series records from the 5–7 March 2016, AR in Bodega Bay, CA. The stable isotope composition of surface vapor along with independent meteorological constraints such as temperature and relative humidity reveal that rainout and post-condensation processes dominate during different portions of the event. We find that Rayleigh distillation controls during peak AR conditions (with peak rainout of 55%) while post-condensation processes have their greatest effect during periods of decreased precipitation on the margins of the event. These results and analyses inform critical questions regarding the temporal evolution of AR events and the physical processes that control them at local scales.