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迂回的路径而闻名，水分通过这些路径到达该地区，然后以雨或雪的形式降落。一些水分来自亚马逊东部，但随着亚马逊空气越过高山到达西部山坡，大部分水分损失了。水汽也来自北部，跟随着从哥伦比亚和委内瑞拉的地点沿着科迪勒拉流动的低空急流。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。根据该奖项进行的工作考虑了通过观察在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地区和旅行历史的程度。这里的同位素组成指的是含有氢、氧-17或氧-18的水分子的相对丰度。氢和氧的同位素较重的水分子蒸发更慢，更容易凝结，因此水蒸气会耗尽较重的同位素，从而使降水沿其传输路径发生。以前的工作表明，使用同位素组成作为水分路径的标志是有希望的，但这些努力没有充分捕捉到起源于东太平洋并向上移动到采集点的水分的同位素特征。正在形成的厄尔尼诺现象提供了一个很有希望的机会来采样起源于太平洋的雨水，特别是在厄尔尼诺的高峰期出现在12-2月季节，与南美夏季季风重合的时候。此外，2023/24年的厄尔尼诺事件预计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演的条件。在这种情况下采样是可取的，因为几乎没有时间执行必要的组织和后勤任务，以便能够进行采样，这是使用快速机制颁发该奖项的基础。鉴于秘鲁西部安第斯山脉是一个水资源有限的地区，因此容易发生干旱，以及伴随着过度降雨而来的泥石流和洪水，这项工作具有社会和科学意义。雨水收集地点是与包括学者和当地志愿者在内的秘鲁同事合作开发的，研究成果将在秘鲁境内传播。此外，该项目还为一名研究生和两名本科生提供支持和培训。另一个考虑是，成功的结果将使同位素签名能够更广泛地用于理解水文循环并验证其模型模拟。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.