RAPID: Measuring the Isotopic Fingerprint of the South American Summer Monsoon during a Strong El Nino, 2023-2024

秘鲁安第斯山脉的西坡以其迂回的路径而闻名，水分通过这些路径到达该地区并以雨或雪的形式落下。 一些湿气来自东部的亚马逊河，但是当亚马逊河的空气上升越过高山到达西部斜坡时，大部分湿气就消失了。 水汽也来自北方，跟随着从哥伦比亚和委内瑞拉沿沿着流动的低空急流。 其他路径从南部和东部到达，在所有情况下都受到山脉的阻挡和引导作用的深刻影响。该奖项下进行的工作考虑了通过查看秘鲁安第斯山脉西侧收集的雨水的同位素组成来确定水分来源区域和迁移历史的程度。 这里的同位素组成是指含有氘、氧-17或氧-18的水分子的相对丰度。 具有较重氢和氧同位素的水分子蒸发得更慢，更容易凝结，因此水蒸气变得缺乏较重的同位素，以至于沿着其输送路径发生降水。 以前的工作已经显示出使用同位素组成作为水分路径标记的希望，但是这些努力没有充分捕获来自东太平洋并向上移动到收集点的水分的同位素特征。发展中的厄尔尼诺现象提供了一个有希望的机会来采样太平洋起源的雨水，特别是厄尔尼诺现象的高峰出现在12月至2月的季节，并与南美洲夏季季风相吻合。 此外，预计2023/24年的厄尔尼诺事件将与有记录以来最强的事件一样强烈，因此未来几个月可能会提供十年或更长时间内不会重复的条件。 在这种条件下进行采样是可取的，因为几乎没有时间进行必要的组织和后勤工作，因此需要使用RAPID机制进行采样，这项工作具有社会和科学意义，因为秘鲁西部安第斯山脉是一个水资源有限的地区，因此容易遭受干旱，以及降雨过多带来的泥石流和洪水。 雨水收集站是与秘鲁同事（包括学者和当地志愿者）合作开发的，研究成果将在秘鲁境内传播。 此外，该项目还为一名研究生提供支持和培训，并雇用了两名本科生。 另一个考虑是，一个成功的结果将使更普遍使用的同位素签名作为理解水文循环和验证模型模拟的一种方式。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The western slopes of the Peruvian Andes are remarkable for the circuitous pathways over which moisture travels to get to the region and fall as rain or snow. Some moisture comes from the Amazon to the east, but much of the moisture is lost as Amazonian air ascends over the high mountains to reach the western slopes. Moisture also comes from the north, following the low-level jet that flows along the Cordillera from points in Colombia and Venezuela. Other pathways arrive from the south and east, in all cases profoundly shaped by the blocking and guiding effects of the mountains.Work conducted under this award considers the extent to which the source region and travel history of moisture can be determined by looking at the isotopic composition of rainwater collected in sites on the western side of the Peruvian Andes. Here isotopic composition refers to the relative abundance of water molecules containing deuterium, oxygen-17, or oxygen-18. Water molecules with heavier isotopes of hydrogen and oxygen evaporate more sluggishly and condense more readily, thus water vapor becomes depleted of heavier isotopes to the extent that precipitation occurs along its transport pathway. Previous work has shown promise for the use of isotopic composition as a marker for moisture pathways but these efforts did not adequately capture the isotopic signature of moisture originating in the eastern Pacific and moving upslope to the collection sites.The developing El Nino offers a promising opportunity to sample rainwater of Pacific origin, particularly as the peak of El Nino occurs in the December-to-February season and coincides with the South American Summer Monsoon. Also, the 2023/24 El Nino event is predicted to be as strong as the strongest events on record, thus the next few months may provide conditions that will not be repeated for a decade or more. The desirability of sampling under these conditions, with little time to perform the necessary organizational and logistical tasks to enable sampling, is the basis for making this award using the RAPID mechanism.The work is of societal as well as scientific interest given that the western Peruvian Andes is a region of limited water resources and thus susceptible to drought, as well as the mudslides and flooding that come with an overabundance of rainfall. The rainwater collection sites have been developed in collaboration with Peruvian colleagues including academics and local volunteers, and research findings will be disseminated within Peru. In addition, the project provides support and training to a graduate student and two undergraduates students are employed by the project. A further consideration is that a successful outcome would enable more general use of isotopic signatures as a way of understanding the hydrological cycle and validating model simulations of it.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.